MSK: BOARDS AND BEYOND Flashcards

Question

What is the relationship between anterior shoulder dislocation and axillary nerve injury?

Answer 1

Approximately 5% of anterior shoulder dislocations are associated with axillary nerve dysfunction due to the nerve’s location below the humeral head and around the humerus neck. This injury leads to a loss of sensation over the lateral shoulder. Long-term damage is rare, and patients usually fully recover.

Answer 2

A supracondylar fracture is a fracture of the distal humerus just above the elbow. It accounts for 60% of elbow fractures and typically occurs in children aged 2 to 7 following a fall on an outstretched arm.

Answer 3

The brachial artery and median nerve cross the elbow joint together, making them vulnerable in supracondylar fractures, especially with posterolateral displacement of the humerus. Brachial artery damage can cause decreased or absent radial pulses and/or compartment syndrome due to forearm swelling.

Answer 4

Median nerve injury from a supracondylar fracture leads to decreased sensation and weakness in the wrist flexors, forearm pronators, finger flexors, and thenar muscles.

Answer 5

Medial epicondylitis, or golfer's elbow, is a form of chronic tendinosis characterized by tendon pain and swelling. It results from repetitive movements, often associated with activities like golfing. Poor mechanics and improper equipment may contribute to this condition.

Answer 6

Pain of the lateral epicondyle and proximal wrist extensors that is worse with resisted wrist extension.

Answer 7

A proximal humerus fracture is the third most common fracture in older adults, following hip and distal radius fractures. It primarily affects individuals over 60 years, particularly females and those with low bone density.

Answer 8

Patients present with bony pain, swelling, and ecchymosis on the affected side. They often hold the arm adducted against their side. Obvious deformities may appear if there is an associated shoulder dislocation.

Answer 9

Proximal humerus fractures carry a high risk of complications due to their proximity to the axillary artery, axillary nerve, and brachial plexus. Complications include avascular necrosis, axillary nerve damage (causing deltoid weakness and loss of sensation to the lateral shoulder), and suprascapular nerve damage (affecting supraspinatus and infraspinatus muscle function).

Answer 10

Avascular necrosis, axillary nerve damage (causing deltoid weakness and loss of sensation to the lateral shoulder), and suprascapular nerve damage (affecting supraspinatus and infraspinatus muscle function)

Answer 11

Nonunion (fracture that does not heal, causing long-term symptoms), although brachial plexus injuries may also occur.

Answer 12

Epicondylar fractures of the humerus occur

Answer 13

Thoracic outlet syndrome can be caused by a cervical rib, an extra rib arising from the 7th cervical vertebra. The cervical rib compresses the brachial plexus trunks (C8-T1) along with the subclavian artery and vein within the scalene triangle, leading to neurovascular symptoms.

Answer 14

Patients present with pain, tingling, and weakness in the wrist and hand flexor muscles. Symptoms worsen with arm elevation. While motor symptoms are more common, vascular symptoms may also develop, including arm swelling, hand ischemia (pallor, cool temperature), and weak radial pulses.

Answer 15

Other causes of thoracic outlet syndrome include muscular anomalies and traumatic injuries. Diagnosis is confirmed by imaging, typically CT or MRI.

Answer 16

Treatment options include physical therapy to relieve symptoms and surgical resection of the cervical rib to alleviate compression.

Answer 17

Impaired flexion and extension of the lateral finger and thumb.

Answer 18

Shoulder impingement syndrome is a condition where the rotator cuff muscles, biceps tendon, and subacromial bursa are compressed between the humeral head and the acromion. This compression causes a spectrum of symptoms related to shoulder pain and dysfunction.

Answer 19

Patients with shoulder impingement syndrome typically present with shoulder pain that worsens with overhead activities or when lying on the affected shoulder.

Answer 20

Winging of the scapula is caused by paralysis of the serratus anterior muscle due to damage to the long thoracic nerve. This nerve arises from the fifth, sixth, and seventh cervical roots and innervates the serratus anterior, which stabilizes the scapula.

Answer 21

Patients present with shoulder pain radiating to the arm and scapula, shoulder weakness, and prominent scapular "winging" that becomes most obvious when they extend their arms against a wall.

Answer 22

Injury to the long thoracic nerve can result from anterior shoulder trauma, surgical procedures, or compression (e.g., prolonged backpack use). Most cases from repetitive motion or compression resolve in 6 to 24 months with physical therapy and rest as the primary treatment.

Answer 23

Radial neuropathy at the spiral groove, also known as "Saturday night palsy," is caused by acute radial nerve compression. The radial nerve originates from the posterior cord of the brachial plexus and innervates the triceps and forearm extensor muscles. Common causes include midshaft humerus fractures, prolonged crutch use, and sleeping with arms over a chair.

Answer 24

In axillary injuries, patients present with triceps weakness, difficulty with wrist and finger extension, and decreased sensation in the posterior forearm and dorsal hand. In spiral groove injuries, symptoms include forearm extensor weakness and decreased sensation in the dorsal hand.

Answer 25

Most cases of acute radial neuropathy resolve completely with conservative treatment, including rest, wrist splinting, and physical therapy. Full recovery is expected in most patients.

Answer 26

Erb’s palsy is an upper brachial plexus injury affecting the C5-C6 trunk, commonly caused by birth trauma. The major risk factor is shoulder dystocia, where the baby’s shoulder gets caught against the mother’s pubic bone during vaginal delivery. This injury leads to stretching of the C5-C6 trunk.

Answer 27

Infants with Erb's palsy present with decreased movement in the affected arm, which is typically held adducted and internally rotated. This positioning results from weakness in the deltoid, infraspinatus (C5), and biceps (C6) muscles.

Answer 28

Musculocutaneous neuropathy is often caused by abnormal arm positioning during surgery. The musculocutaneous nerve originates from the lateral cord of the brachial plexus and primarily innervates the biceps muscle.

Answer 29

Patients with musculocutaneous nerve damage present with weakness in elbow flexion and decreased sensation in the lateral forearm.

Answer 30

Musculocutaneous neuropathy can be associated with trauma, shoulder dislocation, and strenuous exercise, especially those activities involving the biceps muscle.

Answer 31

A scaphoid fracture is commonly caused by falling on an outstretched hand. It is the most common carpal fracture and accounts for approximately 10% of all hand fractures.

Answer 32

Patients with a scaphoid fracture typically present with pain in the anatomic snuffbox (located proximal to the base of the thumb) and decreased grip strength.

Answer 33

Most scaphoid fractures occur in the central portion (waist) of the scaphoid, and 20% to 54% of fractures may initially show a negative x-ray. Due to the high false-negative rates, pain in the anatomic snuffbox should be treated as a scaphoid fracture, regardless of initial x-ray findings.

Answer 34

Ulnar neuropathy can be caused by direct pressure from the handlebars of a bicycle, commonly referred to as handlebar palsy. The ulnar nerve and artery pass through Guyon’s canal into the wrist and are susceptible to damage from chronic compression, hamate fractures, and direct trauma.

Answer 35

The ulnar nerve originates from the medial cord of the brachial plexus and innervates the flexor muscles of the forearm, as well as the fourth and fifth fingers.

Answer 36

Patients with ulnar neuropathy at the elbow present with elbow pain, decreased sensation in the ulnar half of the fourth digit and the fifth digit, and decreased grip strength.

Answer 37

Patients with ulnar neuropathy at the wrist present with decreased sensation in the ulnar half of the fourth digit and the fifth digit, as well as weakness in the abduction and adduction of the fourth and fifth digits.

Answer 38

Conservative treatment for ulnar neuropathy is often unsuccessful, leading many patients to require surgical decompression of Guyon’s canal when conservative measures fail.

Answer 39

Carpal tunnel syndrome is caused by compression of the median nerve in the carpal tunnel, leading to sensory symptoms including pain, numbness, and tingling in the first, second, and third digits and the radial half of the fourth digit. Later symptoms may include wrist pain and weakness with thumb abduction and opposition.

Answer 40

The median nerve originates from the lateral and medial cords of the brachial plexus, innervating the wrist flexor/pronators, finger flexors, and thenar muscles. Risk factors for carpal tunnel syndrome include obesity, pregnancy (due to wrist edema), female gender, and chronic diseases such as rheumatoid arthritis, type 1 diabetes (Hemoglobin H1c), and hypothyroidism. In patients with acromegaly, characterized by excess growth hormone, there is an increased incidence of bilateral carpal tunnel syndrome.

Answer 41

In patients with chronic renal failure, carpal tunnel syndrome is caused by β2-microglobulin amyloid deposits in the carpal tunnel, which compress the median nerve. Normally cleared by glomerular filtration, β2-microglobulin accumulates in plasma and tissues (bones, joints, and tendons) in renal failure, forming amyloid deposits that lead to symptoms. The median nerve innervates the wrist flexor/pronators, finger flexors, and thenar muscles. Patients initially experience sensory symptoms like pain, numbness, and tingling in the first, second, and third digits, as well as the radial half of the fourth digit. Later, symptoms progress to wrist pain and weakness in thumb abduction and opposition, often worse on the side with the dialysis catheter and can be bilateral. Additionally, there may be shoulder pain due to accumulation in the rotator cuff muscles.

Answer 42

A torus (buckle) fracture of the radius is caused by axial force trauma, such as falling onto an outstretched arm. These fractures are most common in young children and typically occur in the distal metaphysis, where the bone is more porous. Torus fractures result from buckling of the cortex due to bony failure and are most often seen in the radius. Patients typically present with tenderness over the wrist, but there is usually no visible swelling or deformity, and they maintain a normal range of motion.

Answer 43

Klumpke's palsy is a lower brachial plexus injury affecting the C8-T1 trunk, typically caused by excessive abduction of the arm, such as attempting to catch a tree branch while falling. Patients with this injury exhibit a "clawed hand" appearance, characterized by hyperextension of the metacarpophalangeal (MCP) joints and flexion of the interphalangeal (IP) joints. This condition leads to impaired function of the intrinsic hand muscles, including the thenar, hypothenar, interosseous, and lumbrical muscles.

Answer 44

Proximal median neuropathy is caused by a laceration above the elbow affecting the median nerve, which originates from the lateral and medial cords of the brachial plexus. This nerve innervates the wrist flexor and pronator muscles, finger flexors, and thenar muscles. Proximal median neuropathy presents with impaired flexion of the first, second, and third digits, a condition known as "Pope's blessing" or the "Hand of Benediction." Patients may also experience impaired thumb abduction and opposition, leading to thenar atrophy, termed "ape hand." Unlike other neuropathies, median neuropathy is not associated with impaired sensation or ulnar deviation, as the flexor muscles of the wrist remain intact. Damage can occur due to supracondylar fractures, carpal tunnel syndrome, or direct trauma to the wrist.

Answer 45

A supracondylar fracture is the most common pediatric elbow fracture, typically caused by a fall onto an outstretched arm. It can damage both the brachial artery and median nerve, which travel across the elbow. The median nerve, arising from the lateral and medial cords of the brachial plexus, innervates wrist flexors, pronators, finger flexors, and thenar muscles. Injury to the median nerve at the elbow results in: - Loss of forearm flexion and pronation - Decreased sensation in the wrist flexors, finger flexors, and thenar muscles - Clinical signs: supinated forearm, ulnar deviation of the wrist, and impaired wrist flexion. - This injury is associated with pain, swelling, and decreased range of motion at the elbow.

Answer 46

Definition: Damage to the recurrent branch of the median nerve, often caused by a superficial hand laceration.

Answer 47

Pathophysiology: The recurrent branch of the median nerve provides motor innervation to the thenar muscles, including the flexor pollicis brevis, abductor pollicis brevis, and opponens pollicis. Injury to this nerve affects thumb movements, particularly abduction and opposition, as the thenar muscles are responsible for these functions.

Answer 48

Clinical Presentation: Impaired thumb movements, specifically loss of abduction and opposition (immobilized thumb). Normal sensation is preserved in the hand, as sensory branches are unaffected. Patients often report difficulty with tasks that require thumb mobility, but there is no sensory loss in the affected hand.

Answer 49

Definition: Genitofemoral neuropathy is a complication of open abdominal surgery, particularly when the genitofemoral nerve is damaged during dissection of the external iliac lymph nodes or mobilization of the iliac vessels.

Answer 50

Pathophysiology: The genitofemoral nerve originates from the L1-L2 trunks of the lumbar plexus. It innervates the cremasteric muscle and provides sensory input to the anterior thigh and scrotum (or labia in females). During abdominal surgery, the nerve is at risk of compression or transection, especially by retractor blades.

Answer 51

Clinical Presentation: - Absent Cremasteric Reflex: Normally, stroking the inner thigh causes the scrotum to rise, but this reflex is absent in genitofemoral neuropathy. - Decreased Sensation: Affected areas include the anterior thigh and the scrotum in males (or labia in females).

Answer 52

Lateral femoral cutaneous neuropathy, or meralgia paresthetica, is a compression neuropathy of the lateral femoral cutaneous nerve (L2-L3), often associated with pregnancy, obesity, or tight clothing.

Answer 53

The lateral femoral cutaneous nerve is a sensory nerve from the lumbar plexus that supplies the anterior and lateral thigh. It passes beneath the inguinal ligament, where it is prone to compression due to pregnancy, tight clothing, tool belts (e.g., in construction workers), or abdominal fat in obesity.

Answer 54

Sensory Symptoms: Pain, numbness, and tingling in the anterior and lateral thigh. Sensory Loss: Possible loss of sensation on the lateral thigh. Management:

Answer 55

Usually self-limited, symptoms often improve with loose clothing, weight loss, or after pregnancy.

Answer 56

Pudendal neuropathy is a nerve injury commonly associated with stretching of the pudendal nerve during vaginal childbirth.

Answer 57

The pudendal nerve originates from S2-S4 of the sacral plexus. It provides motor innervation to the external urethral and anal sphincters and perineal muscles and sensory innervation to the perineum.

Answer 58

Sensory Impairment: Reduced sensation in the perineal area. Incontinence: Possible fecal and urinary incontinence due to sphincter dysfunction. Pain: Dyspareunia (painful intercourse) and perineal pain that worsens with prolonged sitting.

Answer 59

Symptom Relief: Pain management and physical therapy are often recommended.

Answer 60

Definition: Common peroneal neuropathy occurs when the common peroneal nerve is compressed, often due to a tight lower leg cast. Other risk factors include prolonged bed rest, proximal fibular neck fractures, and knee dislocations. Pathophysiology: The common peroneal nerve branches from the sciatic nerve and supplies the short head of the biceps femoris (hamstring muscle) and muscles of the lateral and anterior lower leg. Clinical Presentation: Motor Deficits: Difficulty with dorsiflexion of the foot (leading to foot drop) and toe extension. Sensory Deficits: Decreased sensation over the lateral shin and dorsum of the foot. Management: Removal of Compression: Releasing or loosening casts or other sources of compression. Physical Therapy: Strengthening exercises to help restore movement and function.

Answer 61

Definition: Femoral neuropathy occurs from damage to the femoral nerve (L2-L4) and may result from procedures like inguinal lymph node dissection. Pathophysiology: The femoral nerve originates from the L2-L4 nerve roots of the lumbar plexus and supplies the anterior thigh muscles, including hip flexors and knee extensors.

Answer 62

Clinical Presentation: Motor Deficits: Difficulty with thigh flexion and knee extension. Sensory Deficits: Pain or tingling in the anterior thigh and knee. Reflex Changes: Absent patellar reflex. Management: Physical Therapy: Exercises to improve mobility and strengthen weakened muscles. Pain Management: Medications or modalities to address sensory symptoms.

Answer 63

Definition: S1 nerve root compression occurs as a result of spinal stenosis, most common in individuals over 60. A key risk factor is spondylosis (spinal degenerative arthritis). Pathophysiology: Spinal stenosis involves narrowing of the spinal canal, leading to nerve root compression. Compression Mechanism: Exacerbated in upright posture due to reduced intralaminar space. S1 Compression: Associated with weakness in plantar flexion and diminished ankle reflexes.

Answer 64

Imaging Findings: MRI reveals osteophyte formation and ligamentum flavum hypertrophy. Osteophytes: Bone spurs from chronic arthritis. Ligamentum flavum hypertrophy: Thickening due to inflammatory cell accumulation in chronic osteoarthritis. Clinical Presentation: - Leg Pain: Worsens with standing and walking; relieved by sitting or lying down. Management: - Physical Therapy and Pain Relief: Initial management to address symptoms. - Surgical Intervention: Considered in severe cases for decompression.

Answer 65

L5 radiculopathy is the most common radiculopathy affecting the lumbosacral spine, often caused by herniated discs. Other causes include spondylolisthesis (vertebral displacement) and osteoarthritis.

Answer 66

Herniated Disc: Compresses the L5 nerve root, leading to pain and motor dysfunction. Other Causes: Spondylolisthesis and osteoarthritis may also lead to nerve root compression.

Answer 67

Pain: Lower back pain radiating to the lateral leg and foot. Motor Impairments: Difficulty with foot dorsiflexion and toe extension. Sensory Loss: Decreased sensation along the lateral shin and dorsal surface of the foot

Answer 68

Vs. Common Peroneal Neuropathy: L5 radiculopathy includes radiating lower back pain, while common peroneal neuropathy typically does not.

Answer 69

Conservative Treatment: Rest, physical therapy, pain management. Surgical Options: Considered in severe or refractory cases, often involving decompression.

Answer 70

S1 nerve root radiculopathy is the second most common radiculopathy affecting the lumbosacral spine. The most frequent cause is a herniated disc.

Answer 71

Pain: Lower back pain radiating to the back of the leg. Motor Deficits: Impaired plantar flexion (difficulty standing on toes) and knee flexion. Reflex Changes: Absent or reduced ankle reflex. Sensory Loss: Decreased sensation to the posterior calf and lateral foot.

Answer 72

EMG studies show impairment in muscles innervated by the S1 nerve root, including the gluteus maximus and quadriceps.

Answer 73

L3 nerve root radiculopathy is most commonly caused by spinal stenosis or a herniated disc. The L2, L3, and L4 nerve roots overlap significantly and are usually considered as a group that supplies the femoral nerve.

Answer 74

Pain: Lower back pain radiating to the anterior thigh and knee. Sensory Loss: Loss of sensation to the anterior thigh. Motor Deficits: Impaired hip flexion and knee extension. Reflex Changes: Reduced or absent patellar reflex.

Answer 75

EMG studies show impairment in the muscles innervated by the femoral nerve, including the quadriceps and iliopsoas muscles.

Answer 76

Definition: Superior Gluteal Nerve Injury Damage to the superior gluteal nerve can occur as a complication of hip surgery (hip arthroplasty), occurring in up to 3% of cases. This injury can result from hematoma, direct trauma, or ischemia. While injury to the sciatic nerve is most common, superior gluteal nerve injury may also occur.

Answer 77

The superior gluteal nerve arises from the L4-S1 trunks of the sacral plexus and innervates the gluteus minimus and gluteus medius muscles.

Answer 78

Motor Deficit: Impaired hip abduction. Gait Abnormality: Classic Trendelenburg gait due to weakness of the gluteus medius muscle. When stepping on the affected side, the pelvis tilts toward the unaffected side. Patients have difficulty maintaining balance on the affected leg, with the pelvis tilting to the unaffected side to reduce load and pain. The superior gluteal nerve is purely motor, so sensory loss is not a feature of this injury.

Answer 79

Gluteus maximus.

Answer 80

L5-S2 trunks.

Answer 81

It plays a major role in hip extension and external rotation.

Answer 82

Semimembranosus and semitendinosus.

Answer 83

Pain with hip extension and difficulty standing up from a seated position.

Answer 84

A femoral neck fracture can be caused by trauma, such as a motor vehicle accident. Patients typically present with hip pain, decreased range of motion, and, if the fracture is displaced, an externally rotated and shortened leg.

Answer 85

Avascular necrosis of the femoral head is the most common complication, often due to damage to the medial and lateral circumflex femoral arteries that supply blood to the head and neck of the femur.

Answer 86

SCFE is a condition where the metaphysis of the femur displaces posteriorly through the physeal (growth) plate, which is found only in children. This growth plate is a common weak point in pediatric bones.

Answer 87

SCFE occurs most often in overweight children aged 12 to 14. Symptoms include hip, groin, thigh, or knee pain worsened by activity, altered gait, pain with hip abduction, internal rotation, and flexion, but no pain with adduction. There is usually no history of trauma.

Answer 88

Management requires an immediate referral to orthopedic surgery for hip stabilization. Long-term complications may include osteonecrosis (avascular necrosis) and osteoarthritis.

Answer 89

Avascular necrosis is a condition where vascular damage leads to necrosis of bone marrow elements and joint failure. In this patient, it is caused by chronic glucocorticoid use, which may increase bone marrow adipocyte size, blocking venous outflow.

Answer 90

Heavy alcohol use, systemic lupus erythematosus, sickle cell disease, and lysosomal storage disorders.

Answer 91

Patients experience groin pain that worsens with weightbearing and eventually progresses to pain at rest, with pain on hip internal rotation and abduction.

Answer 92

X-rays may show flattening of the femoral head and collapse in severe cases, while MRI can definitively diagnose by showing separation between normal and ischemic bone.

Answer 93

The condition is progressive, leading to joint failure within a few years and usually necessitating hip replacement surgery.

Answer 94

MH is a disorder characterized by excessive skeletal muscle calcium release due to abnormal ryanodine receptors, leading to continuous muscle contraction.

Answer 95

Ryanodine receptors regulate calcium release from the sarcoplasmic reticulum to facilitate muscle contraction. In MH, these receptors abnormally release calcium in response to certain drugs, causing continuous muscle contraction.

Answer 96

Volatile anesthetics like sevoflurane and the depolarizing muscle relaxant succinylcholine.

Answer 97

Prolonged muscle contraction leads to lactic acidosis, rhabdomyolysis (elevated serum creatinine kinase), and hyperkalemia due to potassium release from damaged muscle cells.

Answer 98

MH is a disorder where abnormal ryanodine receptors in muscle cells cause excessive calcium release from the sarcoplasmic reticulum, leading to continuous muscle contraction. It can be triggered by certain drugs in susceptible individuals.

Answer 99

Volatile anesthetics (e.g., sevoflurane) and the depolarizing muscle relaxant succinylcholine can trigger MH. Prolonged muscle contraction leads to lactic acidosis, rhabdomyolysis (elevated creatinine kinase), and hyperkalemia from potassium release by damaged myocytes.

Answer 100

Treatment includes stopping the triggering agent, cooling the patient, and administering dantrolene, which inhibits ryanodine receptors to decrease calcium release from the sarcoplasmic reticulum.

Answer 101

Mitochondria generate ATP via oxidative phosphorylation. Endurance exercise (e.g., running) increases mitochondrial density in skeletal muscle cells, leading to more numerous and larger mitochondria, an adaptation that enhances endurance. In contrast, resistance training (e.g., weight lifting) does not significantly increase mitochondrial density but rather promotes muscle hypertrophy by increasing actin and myosin for greater force generation.

Answer 102

Slow-twitch fibers, or red fibers, are rich in myoglobin and mitochondria, allowing for sustained ATP production and prolonged contractions. They are slow to fatigue, ideal for activities like long-distance running, and store energy as triglycerides for endurance. Paraspinal muscles, crucial for prolonged standing, are high in slow-twitch fibers.

Answer 103

Fast-twitch fibers are pale, contain fewer mitochondria and less myoglobin, and fatigue quickly but can produce powerful, short bursts of contraction. They are used for short, intense movements, like sprinting or hand and eye movements, and are increased with resistance training.

Answer 104

Human muscles contain a mix of slow- and fast-twitch fibers, influenced by genetics. Studies show that endurance athletes generally have a higher proportion of slow-twitch fibers compared to non-athletes, although the exact mechanism by which exercise modifies this fiber mix is still not fully understood.

Answer 105

Muscle contraction begins when a motor neuron depolarizes a skeletal myocyte, causing calcium release from the sarcoplasmic reticulum.

Answer 106

Calcium binds to troponin, which then removes tropomyosin from the myosin binding site on actin, allowing myosin to bind.

Answer 107

Myosin moves along the actin filament, generating force that causes the muscle to contract.

Answer 108

Troponin is a complex of three subunits—troponin C, troponin T, and troponin I—that regulate muscle contraction.

Answer 109

Troponin C binds calcium at the start of muscle contraction, initiating the process.

Answer 110

Troponin T binds to tropomyosin and helps remove it from the myosin binding groove on actin, allowing myosin to bind for contraction.

Answer 111

Troponin I inhibits myosin binding to actin, and this inhibition is lifted when contraction begins.

Answer 112

Diltiazem decreases calcium entry into cardiac myocytes during phase 2 of the action potential, reducing muscle contraction.

Answer 113

Because it decreases calcium entry into myocytes, it reduces contractility and cardiac output, making it a "negative inotrope."

Answer 114

In patients with systolic heart failure, negative inotropes can further reduce cardiac output, potentially leading to cardiogenic shock with symptoms like hypotension and cool extremities.

Answer 115

Diltiazem can decrease the rate of SA node firing, potentially causing bradycardia.

Answer 116

Myocardial ischemia reduces cardiac contractility in the ischemic areas of the left ventricle, decreasing cardiac output and potentially leading to cardiogenic shock, with symptoms like hypotension and cool extremities.

Answer 117

Norepinephrine activates beta-1 adrenergic receptors in cardiac myocytes, increasing the synthesis of cyclic AMP (cAMP), which activates protein kinase A and phosphorylates calcium channels, allowing more calcium to enter cells and increasing contractile force.

Answer 118

Norepinephrine is a vasopressor that causes alpha-mediated vasoconstriction and has inotropic effects (increases contractility via beta-1 activation), helping to raise blood pressure and improve cardiac output in cardiogenic shock.

Answer 119

Dopamine, like norepinephrine, has both vasopressor and inotropic effects and may also be used to treat cardiogenic shock to improve blood pressure and cardiac output.

Answer 120

Relaxation of coronary artery smooth muscle causes vasodilation, which increases coronary blood flow and can relieve chest pain due to ischemia.

Answer 121

Nitrates are converted to nitric oxide (NO) in vascular smooth muscle cells. NO causes smooth muscle relaxation and vasodilation, increasing blood flow to the coronary arteries.

Answer 122

NO activates guanylyl cyclase in vascular smooth muscle cells, increasing cyclic GMP levels. Cyclic GMP activates myosin light chain phosphatase (MLCP), which de-phosphorylates myosin and leads to smooth muscle relaxation.

Answer 123

Unlike other tissues, the lungs respond to hypoxia with vasoconstriction rather than vasodilation, which helps redirect blood to areas with better ventilation.

Answer 124

Chronic hypoxia in COPD leads to vasoconstriction of pulmonary vessels due to reduced nitric oxide synthesis, which normally helps maintain low smooth muscle tone in the lungs.

Answer 125

Nitric oxide is a vasodilator produced by pulmonary endothelial cells to maintain low muscle tone. Its synthesis requires oxygen, so low oxygen levels reduce nitric oxide production, contributing to hypoxic vasoconstriction.

Answer 126

The lungs constrict their blood vessels in response to hypoxia, a process influenced by decreased nitric oxide production and unique to pulmonary circulation.

Answer 127

Amlodipine is a dihydropyridine calcium channel blocker primarily used to treat hypertension. It works by relaxing vascular smooth muscle, which reduces peripheral vascular resistance and lowers blood pressure.

Answer 128

Amlodipine decreases calcium entry into smooth muscle cells, which reduces the activation of myosin light chain kinase (MLCK). With less MLCK activity, there is more de-phosphorylated myosin light chain (MLC), leading to smooth muscle relaxation.

Answer 129

Phosphorylated MLC is associated with contraction, while de-phosphorylated MLC leads to relaxation. Amlodipine decreases MLC phosphorylation by inhibiting calcium-dependent MLCK activity, thus promoting relaxation.

Answer 130

Norepinephrine, a beta- and alpha-adrenergic agonist, is used in septic shock to increase blood pressure through alpha-1 receptor stimulation, leading to vasoconstriction.

Answer 131

Norepinephrine activates alpha-1 receptors on vascular smooth muscle, which are linked to Gq proteins. This triggers phospholipase C, which converts PIP2 to DAG and IP3. IP3 then releases calcium from the sarcoplasmic reticulum, causing smooth muscle contraction and vasoconstriction.

Answer 132

The Gq subtype of G-proteins mediates vasoconstriction in response to various hormones (e.g., norepinephrine, angiotensin II, vasopressin) by activating pathways that lead to smooth muscle contraction.

Answer 133

High sodium intake causes fluid retention, worsening symptoms like pulmonary edema, dyspnea, and peripheral edema, as the impaired left ventricle struggles to handle the increased volume.

Answer 134

In heart failure, RAAS and SNS are activated, causing vasoconstriction and increasing systemic vascular resistance (SVR) through angiotensin II, vasopressin, and norepinephrine.

Answer 135

These receptors activate the Gq protein subtype, which increases phospholipase C activity. This enzyme converts PIP2 to DAG and IP3, with IP3 releasing calcium from the sarcoplasmic reticulum, causing smooth muscle contraction and vasoconstriction.

Answer 136

Gq proteins mediate vasoconstriction in vascular smooth muscle, responding to hormones like angiotensin II, vasopressin, and norepinephrine, and increasing vascular resistance in heart failure

Answer 137

Most patients (80%) are asymptomatic and diagnosed through incidental hypercalcemia on routine labs. Classic symptoms like "stones, bones, groans, and psychiatric overtones" are now rare.

Answer 138

PTH increases calcium levels by stimulating osteoblasts in bone (leading to bone resorption), increasing renal calcium reabsorption, and enhancing vitamin D activation, which boosts GI calcium absorption.

Answer 139

In kidneys, PTH promotes calcium reabsorption and vitamin D activation; in the GI tract, activated vitamin D increases calcium absorption.

Answer 140

It is most commonly due to a parathyroid adenoma, leading to increased PTH secretion and subsequent hypercalcemia.

Answer 141

Achondroplasia is the most common bone dysplasia, causing dwarfism with short arms and legs in proportion to the body. Diagnosis is often made at birth based on short limbs and a large head.

Answer 142

Bone develops through endochondral ossification (long bones from hyaline cartilage) and membranous ossification (flat bones, like the skull, directly from osteoblasts without cartilage involvement).

Answer 143

Achondroplasia involves a gain-of-function mutation in the FGFR3 gene, which inhibits chondrocyte growth, impairing endochondral ossification. This affects long bones but not flat bones like the skull.

Answer 144

A gain-of-function mutation in FGFR3 causes permanent activation of the receptor, which inhibits chondrocyte growth and limits endochondral ossification, leading to shorter long bones.

Answer 145

The classic symptoms include "stones, bones, groans, and psychiatric overtones," but these are rarely seen now; most patients are asymptomatic.

Answer 146

Elevated PTH increases renal calcium reabsorption, vitamin D activation (increasing intestinal calcium absorption), and bone resorption through osteoclast activation, raising blood calcium levels.

Answer 147

Elevated PTH, increased serum and urinary calcium, and low serum phosphate are typical findings.

Answer 148

PTH activates osteoblasts, which release M-CSF and express RANK-L to stimulate osteoclasts, increasing bone resorption and calcium release into the blood.

Answer 149

Paget's disease, or osteitis deformans, is a disorder of abnormal bone remodeling that typically affects the elderly. Common sites include the skull, spine, pelvis, and long bones.

Answer 150

While most patients are asymptomatic, symptoms can include headache or hearing loss from skull involvement, and fractures at affected bones due to abnormal bone structure.

Answer 151

Imaging often shows thickened and abnormal bone structure, particularly in areas of focal overgrowth, such as the skull.

Answer 152

Serum calcium, phosphate, and parathyroid hormone levels are generally normal, but alkaline phosphatase levels are elevated, indicating increased osteoblast activity.

Answer 153

Alkaline phosphatase, produced by osteoblasts, increases due to heightened bone formation and remodeling. It helps create an alkaline environment necessary for calcium deposition in bone.

Answer 154

An endocrine disorder characterized by excessive secretion of parathyroid hormone (PTH) from the parathyroid gland.

Answer 155

- Hypercalcemia: Elevated serum calcium, the hallmark feature of the disease. - Hypophosphatemia: Low serum phosphate due to increased renal phosphate excretion stimulated by excess PTH

Answer 156

Asymptomatic: Most patients are asymptomatic, with diagnosis often made through routine laboratory testing revealing hypercalcemia.

Answer 157

- Bones (Osteitis Fibrosa Cystica): Bone pain from bone resorption. - Stones (Kidney Stones): Development of calcium-based kidney stones due to hypercalcemia. - Moans (Neuropsychiatric Symptoms): Symptoms like depression, confusion, and hallucinations due to high serum calcium. - Groans (Gastrointestinal Symptoms): Symptoms such as nausea, vomiting, and constipation.

Answer 158

- Description: A skeletal condition resulting from untreated primary hyperparathyroidism, characterized by diffuse bone resorption. - Symptoms: Includes bone pain and, in severe cases, fractures. - Imaging Findings: X-rays reveal subperiosteal bone resorption, visible as radiolucent areas (often highlighted by arrows in imaging).

Answer 159

A rare bone disorder characterized by increased bone density, due to defective osteoclast function and impaired bone resorption.

Answer 160

Presentation: Typically presents in infancy with seizures, intellectual disability, hydrocephalus, and cranial nerve palsies due to abnormal skull and bone structure. Inheritance: Autosomal recessive.

Answer 161

- Role of Carbonic Anhydrase II: This enzyme, present in renal tubular cells and osteoclasts, catalyzes the formation of bicarbonate (HCO3) and acid (H+) from H2O and CO2. - Function in Bone Resorption: Osteoclasts require an acidic environment to resorb bone. Carbonic anhydrase II deficiency impedes this, leading to a lack of acid production and, consequently, impaired bone resorption.

Answer 162

Paradoxical Bone Fragility: Although bones become denser, they are excessively rigid and prone to fracture.

Answer 163

A bone disorder resulting from calcium deficiency, often due to insufficient intake or metabolism of 25-OH vitamin D, leading to impaired bone mineralization and abnormal development.

Answer 164

- Genu Varum: Bowed legs due to weak and improperly mineralized bones. - Rachitic Rosary: Costochondral beading caused by cartilage overgrowth at the costochondral junctions.

Answer 165

- Stage 1 - Vitamin D Deficiency and Hypocalcemia: Insufficient levels of 25-OH vitamin D impair calcium absorption from the intestines, leading to low serum calcium. - Stage 2 - Compensatory Hyperparathyroidism and Hypophosphatemia: Elevated parathyroid hormone (PTH) compensates by increasing renal calcium reabsorption and promoting phosphate excretion, causing hypophosphatemia. Serum calcium may normalize in this stage due to PTH’s effects. - Stage 3 - Severe Hypocalcemia and Hyperparathyroidism Limitations: Calcium levels fall again as hyperparathyroidism can no longer compensate for the significant calcium deficit. Clinical and radiological findings, such as severe bowing and rachitic rosary, become prominent.

Answer 166

Indicates high bone turnover, commonly elevated in patients with rickets.

Answer 167

A condition characterized by decreased bone mineral density, often occurring in postmenopausal women or in patients taking glucocorticoids.

Answer 168

Dual-Energy X-ray Absorptiometry (DXA) Scan: Used to diagnose osteoporosis. A T-score less than -2.5 indicates osteoporosis.

Answer 169

Osteoblast vs. Osteoclast Activity: Osteoporosis involves decreased osteoblast (bone formation) activity and increased osteoclast (bone resorption) activity. This imbalance leads to progressive loss of bone mineral density over time.

Answer 170

- Role in Osteoclast Activation: RANK-L is a protein on osteoblast surfaces that activates osteoclasts, increasing bone breakdown. - Effect on Bone Density: Increased RANK-L activity is associated with higher osteoclast activity and contributes to the reduced bone density observed in osteoporosis.

Answer 171

- Bone Changes in Paget's Disease: Increased Bone Mass: Affected bones have increased density but are structurally abnormal and functionally weak. - Histological Appearance: Bone shows a "mosaic pattern" with thick cement lines marking disorganized lamellar bone. Pathophysiology and Cellular Findings: - Osteoclast Dysfunction: Thought to be primarily a disease of osteoclasts. Affected bones show increased osteoclast numbers with abnormal nucleoli and inclusion bodies in the nuclei, indicating dysfunctional bone resorption.

Answer 172

- Laboratory Findings: Normal Calcium, Phosphate, and Alkaline Phosphatase Levels: These are not typically altered in osteoporosis, as the condition primarily involves a reduction in bone density, not abnormal bone turnover. - Pathophysiology: Characterized by decreased osteoblast (bone formation) activity and/or increased osteoclast (bone resorption) activity, leading to bone fragility and increased risk of fractures.

Answer 173

Mechanism: - Phenytoin activates the cytochrome P450 enzyme system, which increases the catabolism of vitamin D. - This leads to decreased 25-OH-vitamin D levels, which impairs calcium and phosphate absorption in the intestines. Result: - Hypocalcemia and hypophosphatemia occur due to decreased calcium absorption. - Increased parathyroid hormone (PTH) secretion further contributes to bone resorption, resulting in low bone mass.

Answer 174

Condition: Risk of Bone Loss with Antiepileptic Drugs (AEDs) - AEDs Involved: Phenytoin, carbamazepine, phenobarbital - Bone Loss Mechanism: AEDs that induce the cytochrome P450 enzyme system increase vitamin D metabolism, leading to vitamin D deficiency. - Vitamin D deficiency causes hypocalcemia, which activates parathyroid hormone (PTH), promoting bone resorption and reducing bone density. Key Takeaway: - Patients on long-term AED therapy are at higher risk of accelerated bone loss and osteoporosis. Regular monitoring of bone health is recommended.

Answer 175

- Purpose: DXA scans are used to measure bone mineral density (BMD) and diagnose osteoporosis. - Method: A low-energy x-ray beam is attenuated by both bone and soft tissue. A high-energy x-ray beam is attenuated only by bone. - T-Score Calculation: The T-score is calculated by comparing the patient’s BMD to the mean BMD of healthy, age- and ethnicity-matched controls. A T-score of -2.5 or lower indicates osteoporosis.

Answer 176

Bone Types: - Trabecular bone: Porous internal bone (affected more by osteoporosis). - Cortical bone: Dense outer bone. Osteoporosis Impact: Trabecular bone is more affected, leading to fractures in areas with high trabecular content (e.g., spine, hip, wrist). Fracture Risk: - Hip BMD is the most reliable predictor of fracture risk. - Spine BMD is effective for monitoring treatment and will show changes earlier than other sites.

Answer 177

Diagnosis: - Based on a fragility fracture (fracture from minimal force, e.g., fall from standing height). - Or a T-score of -2.5 or lower, measured by dual-energy x-ray absorptiometry (DXA).

Answer 178

- Lifestyle Modifications for Osteoporosis Treatment: Adequate calcium and vitamin D intake. - Weight-bearing exercise (walking, jogging, climbing stairs, tennis, dancing). - Smoking cessation and avoiding heavy alcohol use. - Effect of Weight-Bearing Exercise: Increases bone density and decreases hip fracture risk. Works by stressing bones and stimulating bone formation.

Answer 179

- Demographic Risk Factors: Female sex (most important risk factor). Age (older age increases risk). White race (higher risk compared to other races). - Sex Differences in Bone Density: Osteoporosis is four times more common in women than men. Women achieve peak bone density earlier than men and have lower bone density.

Answer 180

Bisphosphonates for Osteoporosis Treatment: First-line treatment for osteoporosis (e.g., alendronate, risedronate, zoledronate). - Osteonecrosis of the Jaw (ONJ): A rare but serious complication, characterized by pain, swelling, exposed bone, and local infection. - Risk Factors for ONJ: Intravenous bisphosphonate use. Concomitant glucocorticoid therapy, prior dental disease, smoking, and diabetes.

Answer 181

- Bisphosphonates: Structural analogs of pyrophosphate. - Action on Bone: Bind to calcium in hydroxyapatite on bone surfaces, especially in areas of active remodeling. When osteoclasts resorb bone containing bisphosphonates, the drug is released into the osteoclasts. - Effects on Osteoclasts: Impair osteoclast function, reducing bone resorption. - Decrease osteoclast adherence to bone surfaces, further inhibiting resorption. - Outcome: Leads to increased bone mass by inhibiting bone resorption.

Answer 182

- Alendronate: An oral bisphosphonate used in the treatment of osteoporosis. - Effect: Increases bone mass by inhibiting osteoclast-mediated bone resorption. - Common Side Effects: Includes the rare but serious complication osteonecrosis of the jaw (ONJ), especially with high-dose intravenous formulations.

Answer 183

Indication: Teriparatide is recommended for patients with osteoporosis who cannot tolerate bisphosphonates or have contraindications (e.g., achalasia, Barrett’s esophagus, esophageal strictures, gastroesophageal reflux disease). Mechanism: Teriparatide is a recombinant form of parathyroid hormone (PTH). Action: Intermittent administration stimulates bone formation more than bone resorption by promoting osteoblast formation and inhibiting osteoblast apoptosis.

Answer 184

Risk of Osteosarcoma: A 2002 study in rats showed a dose- and duration-dependent increase in osteosarcoma development with long-term PTH administration. FDA Approval: Teriparatide is approved for a maximum duration of two years due to the potential risk of osteosarcoma. Rarity of Osteosarcoma in Humans: Only three cases have been reported in the US.

Answer 185

- Metastasis Location: The diaphysis (mid shaft) of the bones, particularly the axial skeleton (e.g., lumbar spine), is the most common site of metastases in prostate cancer. - Presentation: Patients may present with insidious onset of back pain, pathologic fractures, or spinal cord compression. - Bone Lesions: Prostate cancer typically causes osteoblastic bone lesions (new bone deposition), which appear white on x-rays. Other malignancies associated with osteoblastic lesions include small cell lung cancer, Hodgkin’s lymphoma, and medulloblastoma.

Answer 186

- Symptoms: A compression fracture presents as acute lower back pain, often following bending, coughing, or lifting. - Pain Characteristics: The pain is exacerbated by prolonged sitting and usually does not radiate to the legs. - Risk in Prostate Cancer: Metastatic prostate cancer often leads to bone weakening, increasing the risk for compression fractures, especially in the lumbar spine.

Answer 187

- Location: Ewing sarcoma most commonly occurs in the axial skeleton (pelvis, ribs, spine) and femur. - Symptoms: Patients present with localized pain, swelling, warmth over affected bones, and may develop systemic symptoms such as fever and leukocytosis. Pain increases over time, is worse at night, and is aggravated by exercise. - X-ray Findings: Characteristic “onion skin” appearance, with layering near the periosteum and splitting of the cortex.

Answer 188

- Genetic Translocation: Most cases are associated with a t(11;22) translocation, fusing the EWSR1 gene on chromosome 22 with the FLI1 gene on chromosome 11. This results in aberrant cell growth and proliferation. - Diagnosis: Confirmed histologically by the presence of undifferentiated neuroectodermal cells. - Treatment: Systemic chemotherapy is used in all patients, as subclinical metastases are common.

Answer 189

Location: Osteoid osteomas most commonly occur in the femur, tibia, or spine, typically in boys during their second decade of life. Symptoms: Patients present with bone pain and swelling, which is worse at night and responds to non-steroidal anti-inflammatory drugs (NSAIDs). X-ray Findings: A small central lucency (dark area) surrounded by a sclerotic margin and cortical thickening.

Answer 190

Treatment: Options include observation (as these tumors often resolve spontaneously) or surgical resection. Differentiation from Osteoblastoma: Osteoid osteomas are smaller (less than 2 cm) and have a characteristic response to NSAIDs, whereas osteoblastomas are larger and do not respond to NSAIDs.

Answer 191

- Common Locations: Osteosarcomas typically occur in the metaphysis of long bones, most often affecting the proximal humerus, femur, and tibia. - Symptoms: Patients present with a painful, enlarging mass and may develop pathologic fractures. - Risk Factors: Bimodal age distribution (75% in patients under 20, 25% in older adults), Paget’s disease, prior radiation exposure, and familial cancer syndromes like Li Fraumeni syndrome.

Answer 192

- X-ray Findings: Classic findings include a Codman triangle (tumor breaking through cortex and lifting the periosteum) and a “sunburst” appearance (due to tiny bone fibers in the periosteum). - Treatment: Osteosarcoma is treated with surgical resection and chemotherapy due to the high risk of metastases.

Answer 193

Key Features: Gardner syndrome is characterized by familial adenomatous polyposis (FAP) and extracolonic growths, such as osteomas. FAP Details: Patients develop hundreds of colonic polyps in early adulthood (second or third decade of life) and face a nearly 100% risk of developing colon cancer if the colon is not removed. Associated Mutation: Gardner syndrome is caused by a germline mutation in the APC (Adenomatous Polyposis Coli) tumor suppressor gene.

Answer 194

- Prevalence: Osteomas are found in 20% of patients with Gardner syndrome. - Location: These benign, painless bone growths typically occur on the skull and mandible.

Answer 195

- Most Common Form: Osteoarthritis (OA) is the most common form of arthritis, with over 30 million people in the US affected. - Common Location: OA most commonly affects the knees. - Symptoms: Knee pain exacerbated by prolonged sitting or climbing stairs, evening joint stiffness (worse later in the day), and knee instability. - Physical Exam: Mild knee effusion, quadriceps muscle weakness/wasting, and decreased range of motion.

Answer 196

- X-ray Findings: Asymmetric joint-space narrowing (worse in the medial knee), osteophytes (bone spurs), and subchondral sclerosis (bone thickening). Key Risk Factor: Obesity is the major modifiable risk factor for OA. Patients with a BMI over 30 kg/m² are 7 times more likely to develop knee OA than those with a normal BMI.

Answer 197

Common Symptoms: Anterior hip pain that worsens with standing and after prolonged walking. Physical Exam: Limited range of motion, pain with internal rotation and flexion, quadriceps muscle wasting. Morning Stiffness: Transient morning stiffness (lasting a few minutes), unlike inflammatory arthritis (e.g., rheumatoid arthritis), where stiffness lasts 30-60 minutes.

Answer 198

Risk Factors: Chronic obesity, female gender, advanced age, and genetics. X-ray Findings: Asymmetric joint-space narrowing, osteophytes (bone spurs), subchondral sclerosis (bone thickening). Treatment: Initial treatments include weight loss, acetaminophen, and NSAIDs for pain control. Intraarticular glucocorticoids, opioids, or total joint replacement may be considered for patients not responding to initial treatments.

Answer 199

Symptoms: Lower back pain radiating to the buttocks, groin, or upper thighs, evening stiffness that worsens with activity. Physical Exam: Lumbar tenderness, pain with prolonged walking, and pain with lumbar spine extension.

Answer 200

MRI Findings: Narrowing of the disc space, subchondral sclerosis, osteophytes (bone spurs), and subchondral cysts (fluid-filled cracks in bone). Treatment: Exercise, weight loss, and pain management (acetaminophen and NSAIDs are first-line treatments).

Answer 201

Symptoms: Monoarticular arthritis, tenderness, erythema, warmth, and restricted motion in the affected joint (most commonly the knee). Risk Factors: Pre-existing joint disease (e.g., patellar fracture, knee osteoarthritis), hematogenous seeding, or direct inoculation of bacteria.

Answer 202

Diagnosis: Joint involves a single site, develops acutely, and synovial fluid is purulent with >50,000 white blood cells/mm³. Treatment: Joint drainage and antibiotics (targeting Staphylococcus and Streptococcus species).

Answer 203

Symptoms: Arthritis primarily affecting the metacarpophalangeal (MCP) joints, without swelling, erythema, or warmth; skin hyperpigmentation, type 2 diabetes, cirrhosis, and cardiomyopathy. Cause: Autosomal recessive disorder with increased intestinal iron absorption and iron deposition in tissues.

Answer 204

- Tests: Elevated serum ferritin and transferrin saturation. Genetic testing confirms the diagnosis. Elevated AST and ALT may indicate liver involvement. - Distinguishing Features: Normal synovial fluid white blood cell count (unlike gout or septic arthritis).

Answer 205

Symptoms: Acute pain, erythema, swelling, and warmth in affected joints (commonly the knee). Episodes of arthritis resolve within days to weeks. Diagnosis: Confirmed by the presence of calcium pyrophosphate crystals on polarizing light microscopy of synovial fluid.

Answer 206

Associated Conditions: Hemochromatosis, hyperparathyroidism, hypomagnesemia, and joint trauma. Key Risk Factor: Patients with hyperparathyroidism are three times more likely to develop CPPD than age-matched controls.

Answer 207

- Symptoms: Joint pain, erythema, swelling, and warmth, most commonly affecting the knees. - Risk Factors: Trauma, surgery (especially parathyroidectomy), and severe medical illnesses. - Demographics: More common in older adults (average age 72), with an equal distribution between males and females.

Answer 208

Confirmation: Identified by the presence of calcium pyrophosphate crystals in synovial fluid. Microscopy: Under polarized light microscopy, crystals are positively birefringent. Crystal Appearance: Parallel to light: Blue Perpendicular to light: Yellow Distinction from Gout: Gout crystals are negatively birefringent and appear yellow when parallel to the light.

Answer 209

- Symptoms: Pain, erythema, swelling, and warmth of joints, most commonly the knee. - Synovial Fluid: Elevated white blood cell count (90% neutrophils), may be blood-stained. Diagnosis: Confirmed by the presence of calcium pyrophosphate (CPP) crystals on polarizing light microscopy. X-ray findings: - Chondrocalcinosis (cartilage calcification). - Signs of osteoarthritis (e.g., subchondral cysts, asymmetric joint-space narrowing).

Answer 210

Acute Attacks: Managed with colchicine and NSAIDs. - Colchicine: Standard for pseudogout prophylaxis in patients with recurrent attacks. Mechanism: Binds to tubulin, preventing microtubule polymerization, which inhibits white blood cell migration and phagocytosis.

Answer 211

Symptoms: Pain, erythema, swelling, and warmth in the affected joint, most commonly the 1st metatarsophalangeal joint. Common Presentation: Monoarticular (one joint), typically occurring at night. Synovial Fluid: Contains monosodium urate crystals (diagnostic). White blood cell count typically ranges from 2,000 to 50,000 cells/mm³.

Answer 212

Serum Uric Acid: Elevated levels are common, though the exact cause of increased uric acid production is not well understood. No Specific Enzymatic Defect: Most patients with gout do not have a known metabolic defect in uric acid metabolism. Initial Episodes: Often linked to increased uric acid production rather than decreased excretion.

Answer 213

Cause: Furosemide (loop diuretic) and thiazide diuretics cause volume depletion, which reduces glomerular filtration rate (GFR). - Effect on Uric Acid: Reduced GFR leads to decreased excretion of uric acid, causing elevated serum uric acid levels, which can trigger gout. - Common in Chronic Use: Patients on long-term diuretic therapy are at higher risk of developing gout due to this effect.

Answer 214

Symptoms: Pain, erythema, swelling, and warmth in the affected joint, most commonly at the 1st metatarsophalangeal joint. Common Presentation: Episodes often occur at night and resolve within days to weeks. Diagnosis: Confirmed by the presence of monosodium urate crystals on polarizing light microscopy of synovial fluid.

Answer 215

Alcohol Consumption: Increases lactic acid production, which competes with uric acid for excretion in the kidneys. Higher lactic acid levels lead to increased uric acid reabsorption, triggering a gout attack. Red Meat Consumption: Rich in purines, which are metabolized into uric acid, increasing the risk of gout flares. Other Risk Factors: Obesity, advanced age, and medications (e.g., thiazide and loop diuretics) also contribute to gout.

Answer 216

Symptoms: Joint pain, erythema, swelling, and warmth, most commonly at night and often in the great toe or knee. Diagnosis: Confirmed by the presence of monosodium urate crystals in synovial fluid. Crystal Characteristics: Negatively birefringent under polarized light; crystals appear yellow when parallel and blue when perpendicular to the light.

Answer 217

Symptoms: Gout usually presents as monoarticular arthritis with pain, erythema, swelling, and warmth. The great toe (podagra) is the most common joint involved, but the knee is also frequently affected. Synovial Fluid Analysis: 2,000-50,000 white blood cells/mm³ in gout. This is in contrast to septic arthritis, where white cell counts exceed 50,000/mm³. Diagnosis: Confirmed by the presence of monosodium urate crystals on polarizing light microscopy from synovial fluid.

Answer 218

Hyperuricemia Causes: Gout is associated with elevated serum uric acid levels, which can result from either increased production of uric acid or decreased excretion by the kidneys. Purine Metabolism: Uric acid is a byproduct of purine metabolism. Purines are nitrogenous bases (adenine and guanine) found in DNA, RNA, and other cellular substances like ATP and cAMP.

Answer 219

- Cause: An X-linked recessive disorder due to absence of hypoxanthine guanine phosphoribosyltransferase (HGPRT) enzyme. - Pathophysiology: HGPRT normally recycles purines (adenine and guanine), and its deficiency leads to increased serum uric acid. Clinical Features: - Gout in teenagers. - Neurologic symptoms including hypotonia, dystonia, and intellectual impairment. - Self-mutilating behaviors (biting lips, fingers). Key Point: The lack of HGPRT activity disrupts the purine salvage pathway.

Answer 220

- Mechanism: Non-competitive xanthine oxidase inhibitor that decreases uric acid by inhibiting the conversion of hypoxanthine to uric acid. - Precaution: Not used during an acute gout attack because a rapid decrease in uric acid can precipitate more urate crystals, worsening the attack. - When to start: Once the acute attack resolves, febuxostat is typically initiated with colchicine or NSAIDs to prevent further attacks.

Answer 221

Gout Association with Diuretics: Loop diuretics (e.g., furosemide) and thiazide diuretics cause volume depletion, reducing glomerular filtration rate (GFR) and decreasing uric acid excretion, which raises the risk of gout. Symptoms of Acute Gout Attack: Joint pain, erythema, swelling, and warmth—most commonly affects the 1st metatarsophalangeal joint or knee. Diagnosis: Confirmed by identifying monosodium urate crystals in synovial fluid under polarizing light microscopy.

Answer 222

- Anti-inflammatory Treatment: First-line options: Glucocorticoids, NSAIDs, and colchicine. - Colchicine Mechanism: Microtubule inhibitor that binds tubulin, preventing its polymerization into microtubules. Effect: Limits white blood cell migration into the joint, reducing inflammation.

Answer 223

- Cause: Tumor lysis syndrome occurs as an oncologic emergency, often following induction chemotherapy for cancers like acute lymphoblastic leukemia (ALL). - Mechanism: Rapid cell lysis releases potassium, phosphate, and nucleic acids into circulation. Nucleic acids break down into uric acid, leading to hyperuricemia and acute kidney injury. Symptoms: Related to electrolyte imbalances: Nausea, vomiting, lethargy, seizures, muscle cramps, cardiac dysrhythmias, tetany.

Answer 224

Hyperphosphatemia: - Malignant cells contain 4x more phosphorus than normal cells, causing high serum phosphate. - Phosphate binds calcium, reducing serum calcium and causing hypocalcemia. - Calcium phosphate crystals may precipitate in the kidneys. Hyperkalemia: - High potassium levels in malignant cells lead to elevated serum potassium following tumor lysis.

Answer 225

Presentation: Gout flares are usually monoarticular (80% of cases) and typically occur at night.

Answer 226

- Xanthine Oxidase Inhibitors: Medications like allopurinol and febuxostat inhibit xanthine oxidase, reducing the conversion of hypoxanthine to uric acid, which helps to lower serum uric acid levels and prevents gout attacks. Interaction with Azathioprine: - Azathioprine is metabolized to 6-mercaptopurine (6-MP), which depends on xanthine oxidase for further breakdown. - Xanthine oxidase inhibitors increase 6-MP levels, potentially causing azathioprine toxicity. Clinical Implication: Azathioprine dosage should be reduced or discontinued in patients taking xanthine oxidase inhibitors.

Answer 227

Probenecid: A sulfa drug that reduces serum uric acid by blocking uric acid reabsorption in the kidney's proximal tubule. Use in Gout: Considered second-line therapy to prevent recurrent gout after allopurinol and febuxostat. Additional Effect: Probenecid can inhibit penicillin secretion in the kidney, thereby increasing penicillin levels. Clinical Application: Occasionally used to enhance penicillin efficacy in neurosyphilis where high serum levels are needed to cross the blood-brain barrier.

Answer 228

Definition: Reactive arthritis is joint inflammation triggered by a prior bacterial infection in the gastrointestinal or genitourinary tract. Common Triggers: Gastrointestinal: Shigella, Salmonella, Yersinia, Campylobacter. Genitourinary: Chlamydia. Onset: Inflammatory symptoms typically begin 1-4 weeks after the infection.

Answer 229

- Joint Symptoms: Inflammation mainly in the lower extremities, often asymmetric; includes dactylitis (swollen fingers/toes) and inflammatory back pain. Other Symptoms: - Ocular: Conjunctivitis or anterior uveitis causing eye pain, redness, blurry vision. - Genitourinary: Urethritis (often asymptomatic in women; may cause pain in men) and cervicitis. Course: Usually self-limited, resolving over months, but some cases may require chronic therapy for persistent symptoms.

Answer 230

Definition: Psoriatic arthritis is a type of arthritis associated with psoriasis, a chronic inflammatory skin condition marked by pink plaques with silver-white scale, often on the elbows, knees, and scalp. - Onset: Arthritis develops in about 15-20% of patients with psoriasis, typically years after skin symptoms appear. - Nail Findings (common in psoriatic arthritis): - Onycholysis (nail detachment) - Subungual hyperkeratosis (scaling under the nail) - Pitting of the nails

Answer 231

- Joint Involvement: Frequently affects the distal interphalangeal (DIP) joints of the hands and feet; usually correlated with nail psoriasis in the same digit. Additional Symptoms: - Dactylitis (swelling of entire fingers or toes) - Enthesitis (inflammation where tendons attach to bones) - Sacroiliitis (inflammation of the sacroiliac joints) - Large Joint Involvement: Commonly affects joints like the knees.

Answer 232

Definition: AS is a chronic inflammatory condition affecting the spine and sacroiliac joints. - Primary Symptom: Persistent back pain. - Radiographic Changes: - Erosions at vertebral corners → vertebral squaring - Syndesmophytes (bony growths from disc ossification) → "bamboo spine" appearance - Progressive fusion of vertebral bodies causing spinal stiffness and limited mobility. Additional Manifestations: - Enthesitis (commonly in the heel) - Uveitis (eye inflammation) - Dactylitis (swelling of entire digit)

Answer 233

- Spinal Progression: Syndesmophytes start in the lumbar region and move upward, leading to spinal stiffness. Chest Involvement: - Costovertebral and costosternal joint inflammation can lead to restricted chest expansion and restrictive lung disease. - Inflammatory Markers: Typically elevated C-reactive protein (CRP). - Genetic Predisposition: Up to 95% of AS patients are HLA-B27 positive, indicating a strong genetic link.

Answer 234

Definition: Crohn's disease is a type of inflammatory bowel disease (IBD) causing chronic inflammation of the gastrointestinal mucosa. Histopathologic Features: - Transmural inflammation (affects the full thickness of the intestinal wall) - Noncaseating granulomas T-cell Involvement: - T-cell-mediated inflammation seen in both the gut mucosa and synovial tissue in joints, linking intestinal and joint inflammation.

Answer 235

IBD-Associated Arthritis: - Pauciarticular type (fewer than five joints) is common, often acute, self-limited, and affects large joints like the knees. - Joint symptoms tend to correlate with IBD activity, worsening during flares and improving with treatment. Extraintestinal Manifestations: - Erythema nodosum (inflammation of subcutaneous fat, usually on the shins) - Uveitis (eye inflammation) - Arthritis Prevalence: ~20% of Crohn's patients develop arthritis.

Answer 236

Definition: Ankylosing spondylitis (AS) is a chronic inflammatory disease causing inflammation of the spine and sacroiliac joints. Key Symptom: Inflammatory back pain—slow onset before age 40, worse at night, and improved with exercise. Other Symptoms: Enthesitis: Commonly in the heel. Dactylitis: Swelling of an entire digit. Uveitis: Up to 40% of AS patients develop anterior uveitis (also called iritis) with symptoms like redness, pain, blurred vision, and photophobia. Genetic Link: Over 90% of patients are HLA-B27 positive.

Answer 237

Diagnosis: - Characteristic Features: Inflammatory back pain, enthesitis, uveitis, elevated C-reactive protein, and family history of spondyloarthritis support AS diagnosis. - Non-Radiographic AS: Patients with HLA-B27 positivity and AS symptoms but without x-ray changes can be diagnosed with non-radiographic AS. Radiographic Findings: - Late Findings: Sacroiliitis, and bamboo spine—characteristic changes often appear years after symptom onset.

Answer 238

Definition: Polymyositis is a chronic autoimmune myopathy that leads to proximal muscle weakness. Cause: Cell-mediated cytotoxic injury to myocytes, involving CD8+ T-cells and macrophages infiltrating the endomysium (connective tissue around each muscle fiber). Symptoms: - Gradual onset of symmetric proximal muscle weakness in arms and legs. - Neck weakness: Can cause dysphagia and difficulty holding the neck up.

Answer 239

Laboratory Findings: - Elevated inflammatory markers: C-reactive protein, erythrocyte sedimentation rate (ESR). - Increased creatine kinase and positive antinuclear antibodies. - Myositis-specific antibodies positive in about 30% of cases. Diagnosis: Muscle biopsy showing endomysial inflammation is the gold standard. Treatment: Immunosuppressants help relieve symptoms, though they do not cure the disease.

Answer 240

Definition: Polymyositis is a chronic autoimmune myopathy that leads to proximal muscle weakness. Cause: Cell-mediated cytotoxic injury to myocytes, involving CD8+ T-cells and macrophages infiltrating the endomysium (connective tissue around each muscle fiber). Symptoms: Gradual onset of symmetric proximal muscle weakness in arms and legs. Neck weakness: Can cause dysphagia and difficulty holding the neck up.

Answer 241

Laboratory Findings: - Elevated inflammatory markers: C-reactive protein, erythrocyte sedimentation rate (ESR). - Increased creatine kinase and positive antinuclear antibodies. - Myositis-specific antibodies positive in about 30% of cases. Diagnosis: Muscle biopsy showing endomysial inflammation is the gold standard. Treatment: Immunosuppressants help relieve symptoms, though they do not cure the disease.

Answer 242

Definition: Juvenile dermatomyositis is an autoimmune myopathy causing symmetric proximal muscle weakness and distinctive skin findings. Typical Age of Onset: Most common in children aged 5–15 years. Cutaneous Hallmarks: - Heliotrope rash: Red or purple discoloration on the upper eyelids, often with periorbital edema. - Gottron’s papules: Red, scaly papules on the extensor surfaces of joints (fingers, elbows, and knees). - Other skin signs: Shawl sign (upper back), V sign (upper chest), and “mechanic’s hands” (thickened, scaly fingers).

Answer 243

Additional Findings: - Calcinosis cutis: Calcium deposits in the skin/subcutaneous tissue, more common in juvenile cases. - Nail fold capillaries: Redness and dilated capillaries visible over nail folds. - Disease Progression: Rash often precedes slow onset of muscle weakness. Contrast with Adult Dermatomyositis: Juvenile form has no association with malignancy.

Answer 244

Definition: Dermatomyositis is an inflammatory myopathy causing symmetric proximal muscle weakness. Histology: CD4+ and B-cells infiltrate the perimysium (connective tissue around muscle fascicles) and small blood vessels. Key Findings: Perimysial and perivascular inflammation with perifascicular atrophy (atrophic muscle fibers at fascicle edges). Muscle Symptoms: Gradual onset of weakness in proximal muscles (e.g., shoulders, hips).

Answer 245

Characteristic Skin Signs: - Heliotrope rash: Red/purple discoloration on upper eyelids with periorbital edema. - Gottron’s papules: Red, scaly papules on extensor surfaces of finger joints. Additional Skin Signs: - Shawl sign: Red/purple macules on the upper back and shoulders. - V sign: Red/purple macules in a V shape on the upper chest. - Mechanic’s hands: Thickened, scaly skin on fingers.

Answer 246

Definition: PMR is an inflammatory condition seen in adults over 50 years. Symptoms: Morning stiffness and pain in the neck, shoulders, and hips that improves as the day progresses. Active range of motion may be limited due to pain. Labs: Normal muscle strength and creatine kinase levels; elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). Treatment: Corticosteroids are typically effective.

Answer 247

Link: PMR is associated with GCA (temporal arteritis) in about 50% of cases. GCA Symptoms: New, frequent headaches; temporal artery tenderness and thickening. Diagnosis: Temporal artery biopsy showing granulomatous inflammation. Treatment: Corticosteroids are also used as main therapy for GCA.

Answer 248

Key Types: Dermatomyositis and polymyositis are common inflammatory myopathies. Antibodies: - ANA (positive in ~80%): Nonspecific, may be positive in other diseases. - Anti-Jo-1 (positive in ~30%): Myositis-specific, directed against histidyl-tRNA synthetase. - Other Myositis-Specific Antibodies: Anti-Mi-2 and anti-SRP. Clinical Relevance: Anti-Jo-1 antibodies indicate a higher risk of pulmonary disease and poorer corticosteroid response.

Answer 249

Anti-Jo-1: Associated with pulmonary disease risk and lower corticosteroid response. Anti-Mi-2: Linked to a better prognosis and good response to corticosteroids.

Answer 250

Mechanism: Autoantibodies target presynaptic voltage-gated calcium channels, reducing calcium influx. Effect: Less calcium causes decreased acetylcholine release at neuromuscular junctions, leading to muscle weakness. Key Signs: Gradual proximal weakness, especially in lower extremities, and diminished or absent deep tendon reflexes.

Answer 251

- Autonomic Symptoms: Dry mouth, constipation, and erectile dysfunction due to impaired autonomic signaling. - Electrophysiology: High-frequency stimulation shows improved neurotransmission as more acetylcholine vesicles are released. - Exercise Effect: Temporary improvement in muscle strength and reflexes with exercise.

Answer 252

Cause: Autoimmune disease with antibodies against postsynaptic acetylcholine receptors, blocking acetylcholine binding and leading to muscle weakness. Initial Symptoms: Commonly affects ocular muscles, causing asymmetric ptosis (drooping eyelid) and diplopia (double vision). Progression: Begins as ocular myasthenia gravis; may progress to generalized MG affecting proximal muscles symmetrically, with worsening symptoms upon repetitive use.

Answer 253

- Tensilon Test: Uses edrophonium, a short-acting acetylcholinesterase inhibitor, to temporarily improve muscle strength, aiding MG diagnosis. - Standard Therapy: Long-acting AchE inhibitors like pyridostigmine are used for ongoing symptom management. Generalized MG Symptoms: Weakness can extend to facial muscles, causing drooping mouth, difficulty speaking, and difficulty swallowing.

Answer 254

Cause: Autoantibodies against presynaptic voltage-gated calcium channels reduce acetylcholine release at neuromuscular junctions, leading to proximal muscle weakness. Symptoms: Includes autonomic dysfunction (e.g., dry mouth, constipation), reduced deep tendon reflexes, and improved muscle strength with exercise.

Answer 255

SCLC Link: Up to 60% of LEMS patients have SCLC, with tumor cells expressing VGCC that can trigger LEMS-causing antibodies. Diagnosis & Treatment: LEMS symptoms often precede lung cancer symptoms; treating SCLC can improve LEMS symptoms.

Answer 256

Cause: Autoantibodies against acetylcholine receptors (AchR) at neuromuscular junctions, disrupting transmission and causing weakness. - Association: Early-onset MG often includes thymic hyperplasia (enlarged thymus with germinal centers producing AchR antibodies).

Answer 257

- Thymic Hyperplasia: Found in early-onset MG; includes B-cell proliferation in thymus. - Thymoma: Affects up to 10% of MG patients; thymic tumor producing AchR antibodies. Treatment: Thymectomy (surgical removal of the thymus) can benefit patients with AchR antibodies and thymic abnormalities.

Answer 258

Definition: Overstimulation of acetylcholine receptors due to excess acetylcholine, leading to muscle weakness and autonomic symptoms. - Causes: Can result from overdose of acetylcholinesterase inhibitors like pyridostigmine in myasthenia gravis patients, or organophosphate poisoning.

Answer 259

Neuromuscular Symptoms: Muscle weakness, fasciculations (muscle twitches). - Autonomic Symptoms: Lacrimation, miosis (pupil constriction), salivation, diaphoresis (sweating), bronchospasm, bronchorrhea (excess bronchial secretions), diarrhea, bradycardia, and urinary frequency.

Answer 260

- Atropine: Muscarinic antagonist used to reduce autonomic symptoms like bronchoconstriction, bradycardia, and salivation. It does not affect skeletal muscle (nicotinic receptors). - Pralidoxime: Effective in organophosphate poisoning as it reactivates acetylcholinesterase by displacing organophosphates. It is not effective in pyridostigmine overdose.

Answer 261

- Respiratory Distress Causes: Due to respiratory muscle weakness, bronchospasm, and increased bronchial secretions. - Intervention: Mechanical ventilation may be required to support respiration until muscle function recovers.

MSK: BOARDS AND BEYOND Flashcards

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