Uworld21 Flashcards
What is catscratch disease?
caused by Bartonella henselae, a gram negative coccobacillus transmitted by a cat scratch or bite.
Patients commonly present with tender lymphadenopathy proximal to the inoculation site (eg, axillary, epitrochlear lymph nodes).
Lymph node histopathology often shows necrotizing granulomas and stellate shaped microabscesses.
What is leptin?
Leptin is a protein hormone produced by adipocytes in proportion to the quantity of fat stored.
Leptin acts on the arcuate nucleus of the hypothalamus to inhibit production of neuropeptide Y (decreasing appetite) and stimulate production of alpha-MSH (increasing satiety).
Mutations in the leptin gene or receptor result in hyperphagia and profound obesity
Damage to the subthalamic nucleus causes?
The subthalamic nucleus plays an important role in the modulation of basal ganglia output.
Damage to this structure (eg, due to lacunar stroke) may result in contralateral hemiballism: wild, involuntary, large-amplitude, flinging movements of the proximal limbs (arm and/or leg) on one side of the body
What test is specific for EBV?
Epstein Barr virus commonly infects B cells, stimulating them to proliferate continuously (transformation or immortalization).
EBV is an oncogenic virus that promotes polyclonal B cell proliferation and heterophile antibody production.
The heterophile antibody test is sensitive and highly specific for EBV infection
Temporal lesions can cause what eye issue?
The inferior optic radiations travel through the temporal lobe in the Meyer loop.
They carry information from the inferior retina, which covers the superior visual field. Therefore, temporal lobe lesions can result in contralateral homonymous superior quadrantanopia.
What is gestational thrombocytopenia?
common in the third trimester and is typically mild, asymptomatic, and not associated with other laboratory abnormalities. It occurs due to hemodilution (ie, maternal plasma volume expansion) and increased sequestration/consumption of platelets in the placenta.
What drugs have the highest risk for drug induced lupus?
Procainamide and hydralazine and isoniazid.
Drug induced lupus has positive ANA and anti-histone antibodies.
Classic galactosemia results from deficiency of?
galactose-1-phosphate uridyl transferase.
Clinical features: vomitting, lethargy, jaundice, and E coli sepsis.
Cessation of breastfeeding and switching to soy milk based formula is recommended
What is negative predictive value?
represents the probability of not having a disease given a negative test result.
NPV is inversely proportional to the prevalence of a disease.
When a patient has characteristics similar to the overall population (eg, age, sex, risk factor status), the disease prevalence is a valid estimate of the pretest probability of disease
The infusion of excessive normal saline (sodium chloride) is a common cause of?
nonanion gap metabolic acidosis.
The excess intravascular chloride causes intracellular shifting of bicarbonate, reducing serum bicarbonate and decreasing blood pH
What is renal artery stenosis?
Marked unilateral kidney atrophy is suggestive of renal artery stenosis.
It occurs in elderly people due to atherosclerotic narrowing of the renal artery and is often seen in association with other atherosclerotic risk factors or diseases (eg, chronic mesenteric ischemia, coronary artery disease, peripheral vascular disease).
Hypertension and abdominal and flank bruits are often present.
What is hypoglycemia characterized by?
tremor, diaphoresis, and confusion in association with a low blood glucose level and resolution of symptoms when the blood glucose level is corrected.
Hypoglycemia with elevated insulin and low C peptide levels suggests exogenous insulin injection, whereas elevated C peptide suggests an insulin secretagogue or insulin secreting tumor
What is paroxysmal noctural hemoglobinuria?
Triad of hemolytic anemia, hypercoagulability, and pancytopenia.
PNH results from an acquired mutation in the PIGA gene that causes absence of the glycosylphosphatidylinosital anchor and associated deficiency of CD55 and CD59 complement inhibitor proteins
What can cause watershed infarctions?
Sustained cerebral hypoperfusion (eg, hypotension, shock) may cause cerebral ischemia and watershed infarction.
These watershed zones are located at the borders between areas perfused by the anterior, middle, and posterior cerebral arteries and typically appear as symmetric, bilateral wedge shaped strips of necrosis over the cerebral convexity, parallel and adjacent to the interhemispheric fissure.
Which heme drugs effect thrombin time and which do not?
Direct factor Xa inhibitors (apixaban, rivaroxaban) increase the prothromin and activated thromboplastin times but do not affect the thrombin time.
Unfractionated heparin and direct thrombin inhibitors (dabigatran) prolong the thrombin time.
Why does appendicitis cause pain?
Appendicitis causes dull visceral pain at the umbilicus due to afferent pain fibers entering at the T10 level in the spinal cord.
Progressive inflammation in the appendix irritates the parietal peritoneum and abdominal wall to cause more severe somatic pain shifting from the umbilicus to McBurney’s point (2/3 of the distance from the umbilicus to the anterior superior iliac spine)
What is serum sickness?
an immune complex mediated type III HSR that typically forms 5-14 days after exposure to foreign proteins in an antitoxin, antivenom, monoclonal antibody, or vaccine.
Patients typically develop fever, urticarial rash, and arthralgia that resolve spontaneously over days as the immune complexes are cleared by the mononuclear phagocyte system
Which holosystolic murmur increases in intensity on inspiration?
tricuspid regurgitation.
CD4 binds which HIV receptor
gp120
CD21 likes to bind which receptor
epstein barr gp350
erythrocyte P antigen likes to bind?
parvovirus B19
What is ovarian torsion?
typically occurs in reproductive aged women due to rotation of the ovary around the infundibulopelvic (suspensory) and uteroovarian ligaments.
Patietns typically have sudden onset unilateral pelvic pain and a tender adnexal mass.
MOA of phenoxybenzamine
irreversible alpha 1 and 2 antagonist that effectively reduces the arterial vasoconstriction induced by norepinephrine
Because phenoxybenzamine is an irreversible antagonist, even very high concentrations of norepi, such as in pheochromocytoma, cannot overcome its effects
What leads to muscle fiber type grouping?
With muscle denervation and reinnervation, nerve fiber collateral sprouting results in adjacent muscle fibers being innervated by the same neuron.
This leads to loss of the normal histologic checkerboard pattern of type 1 and type 2 muscle fibers and results in muscle fiber type grouping
What is Ewing sarcoma?
malignant bone tumor that typically arises in the long bones or pelvis in children and often mets to the lungs.
Imaging: poorly defined, lytic lesion with an onion skin periosteal reaction.
Histopath: sheets of uniform small round blue tumor cells
Thiazide and loop diuretics electrolytes status
Thiazide and loop diuretics causes significant volume depletion, activating the renin-angiotensin-aldosterone system, which can lead to hypokalemia and metabolic alkalosis.
Thiazide diuretics are more likely to cause hyponatremia and hypercalcemia; loops cause hypocalemia
How does systemic sclerosis effect the esophagus?
may result in esophageal dysmotility and incompetence of the lower esophageal sphincter due to atrophy and fibrous replacement of the esophageal muscularis. This can cause GERD with an increase risk of Barrett esophagus and stricture formation
Thiazide diuretics, espically metolazone, potentiate the diuretic effect of loop diuretics (eg, furosemide) by?
blocking the reabsorption of the increased distal tubular sodium delivery caused by loop diuretics
Elevated intracranial pressure in the absence of an intracranial mass lesion or ventriculomegaly is suggestive of?
decreased resorption of cerebrospinal fluid. This often occurs when the cerebral venous sinus system drainage is impaired due to either idiopathic intracranial hypertension or cerebral venous sinus thrombosis
Why is drainage of an empyema difficult?
Empyema involves bacterial invasion of the intrapleural space with progressive inflammation, pus accumulation, and organized fibrosis.
Drainage with a chest tube is often difficult due to loculations and high viscosity, but it can be aided by the intrapleural administration of a fibrinolytic agent (eg, tissue plasminogen activator) in combination with a nucleic acic cleaving enzyme (ie, deoxyribonuclease)
What is the most common complication of bicuspid aortic valves?
aortic stenosis.
Patients with bicuspid aortic valves develop clinically significant aortic stenosis on average around age 50.
In comparison, senile calcific stenosis of normal aortic valves generally becomes symptomatic age >65
What kind of laxative is polyethylene glycol?
an osmotic laxative.
Primary lactose intolerance is associated with the inability to digest lactose. The high osmotic load from intraluminal accumulation of lactose can lead to watery diarrhea.
How can Turner syndrome women get pregnant?
In vitro fertilization used a donated ovum is the most promising means of achieving pregnancy in a women with Turner syndrome.
Pregnancy can occasionally occur spontaneously in some patients with Turner syndrome, but the risk of spontanous abortion, Down syndrome and Turner syndrome are all increased in such cases.
Acute myocarditis is most commonly caused by?
a viral infection (coxsackie, adenovirus, influenza)
It often resolves without noticeable symptoms, but patients can develop serious complications, including decompensated heart failure due to dilated cardiomyopathy or sudden cardiac death due to ventricular arrhythmia.
Histopath: myocyte necrosis with inflammatory mononuclear infiltrate
Lupus nephritis occurs due to?
SLE is an autoimmune disease characterized by the formation of antinuclear antibodies (anti-DNA antibodies)
Lupus nephritis occurs primarily due to the formation of immune complexes containing DNA and anti-DNA in the circulation. These are deposited in the glomerulus where they result in complement activation, recruitment of inflammatory cells, and renal injury (type III HSR)
What is the most common neurologic complication of varicella zoster virus infection?
Postherpetic neuralgia
What is a thyroglossal duct cyst?
Failed atrophy of the thyroglossal duct in utero can result in thyroglossal duct cysts that can be located anywhere along the path of thyroid descent (from the tongue base to the thyroid base to the thyroid isthmus).
Anterior midline neck mass that moves superiorly with swallowing or tongue protrusion.
Down syndrome is commonly caused by?
Most commonly caused by maternal meiotic nondisjunction, a process by which the fetus receives 3 full copies of chromosome 21.
Dysmorphic features (flat facial profile, protruding tongue, small ears, upslanting palpebral fissures) and cardiac defects (eg, endocardial cushion defects) are characteristics.
Which cancer is associated with vinyl chloride?
Hepatic angiosarcoma is an aggressive vascular malignancy associated with exposure to carcinogens (eg, vinyl chloride).
The tumor cells express CD31 (ie, platelet endothelial cell adhesion molecule [PECAM1], an endothelial cell marker important for leukocyte transmigration
Which rotator cuff muscles are responsible for external rotation?
The rotator cuff muscles attach to the proximal humerus and move the arm at the shoulder.
Infraspinatus and tere minor are primarily responsible for external rotation. When one is torn, the other hypertrophies to compensate, resulting in preserved strength in external rotation.
What is relative risk?
the measure of assoication between the exposure to a risk factor or treatment and an outcome or disease and is commonly used in cohort studies.
The interpretation of the RR depends on which groups are identified as exposed and unexposed.
