Uworld15 Flashcards
What is deficient in classic galactosemia?
galactose-1-phosphate uridyl transferase deficiency
What is deficient in essential fructosuria?
fructokinase deficiency.
Essential fructosuria is a benign disorder. Although affected patients are asymptomatic, their urine will test positive for a reducing sugar due to the presence of unmetabolized fructose
Deficiency of Vitamin B12 presentation
Vitamin B12 is obtained through the diet solely from animal sources, which places strict vegans at risk for dietary deficiency.
This deficiency takes years to develop due to the large hepatic vitamin B12 reserve, and presents with megaloblastic anemia and potentially irreversible neurologic deficits (eg, paraesthesia, weakness, and ataxic gait)
Mild cognitive impairment vs dementia diagnosis
Mild cognitive impairment is diagnosed when cognitive decline is present but activities of daily living (bathing, preparing meals, managing finances) are preserved.
In contrast, dementia is diagnosed when cognitive decline interferes with activities of daily living.
In patients with recurrent calcium nephrolithiasis, what meds can help prevent stone formation?
Thiazide diuretics effectively increase renal calcium reabsorption; decreasing urine Ca2+ excretion
What is an acoustic neuromas?
Schwanna cell derived tumors that typically arise from the vestibular portion of the vestibulocochlear nerve and are commonly located at the cerebellopontine angle (between the cerebellum and lateral pons).
Patients usually present with unilateral sensorineural hearing loss and tinnitus
What is pityriasis versicolor (tinea versicolor)?
a superficial skin infection caused by Malassezia species.
It causes erythematous, hyper or hypopigmented macules and patches.
Malassezia forms spores and hyphae, producing the characteristic “spaghetti and meatballs” appearance on KOH preparation light microscopy.
How does pregnancy affect respiratory drive?
The normal physiology of pregnancy involves chronic hyperventilation caused by elevated progesterone levels stimulating an increase in central respiratory drive,
This creates an expected respiratory alkalosis with metabolic compensation (increased renal bicarbonate excretion) that helps facilitate the transport of acidic wastes from, and the transport of oxygen to, the developing fetus
MOA of bevacizumab?
a monoclonal antibody that inhibits the binding of vascular endothelial growth factor (VEGF) to its receptor.
This inhibits angiogenesis and limits blood supply to tumors (ie, cancer starving therapy). However, it also impairs wound healing and can lead to wound dehiscence.
What is alternative splicing?
a process where the exons of a gene are reconnected in multiple ways during post-transcriptional processing.
This creates different mRNA sequences and subsequently, different protein isoforms.
It is a normal phenomenon in eukaryotes that greatly increases the biodiversity of proteins encoded by the genome.
What explains the rapid onset of action and short duration of action for propofol?
Propofol and other highly lipophilic drugs readily diffuse across membranes, quickly accumulating in tissues receiving high blood flow; this accounts for their rapid onset of action. These compounds are subsequently redistributed to organs receiving less blood flow, which explains their short duration of action.
Function of glutamate
Glutamate is the main excitatory neurotransmitter of the CNS, inducing postsynaptic neuron depolarization and calcium entry through the NMDA receptor,
Calcium entry programs the neuron to depolarize more robustly to repeated stimulation; this long term potentiation forms a molecular basis for memory, learning, and addiction.
Why are patients with cleft palate are at increased risk of chronic or recurrent acute otitis media?
Partly because of dysfunction of the muscles (eg, levator veli palatini) that contract against the soft palate to open the eustachian tube
What can provide on-site microbiologic confirmation for Group A strep?
Group A Strep (GAS) should be suspected in those with acute-onset sore throat, exudative tonsillopharyngitis, and no evidence of viral symptoms (eg, coryza, cough, conjunctivitis)
In office throat swab with rapid antigen detection testing (immunoassay for GAS antigens) can provide on site microbiologic confirmation, allowing for early initiation of treatment
What is polymyositis?
Polymyositis causes symmetric proximal muscle weakness.
Muscle biopsy reveals inflammation, necrosis, and regeneration of muscle fibers.
Over expression of major histocompatibility complex class I proteins on the sarcolemma leads to infiltration with CD8 T lymphocytes and myocyte damage
What class of drugs is associated with body fat redistribution?
Highly-active antiretroviral therapy (HAART) for HIV is commonly associated with body fat redistribution. Subcutaneous lipoatrophy involving the face and extremities is associated with nucleoside reverse transcriptase inhibitors (especially stavudine and zidovudine) and protease inhibitors. Central fat accumulation in the trunk and viscera can occur with any HAART regimen.
Cleft lip occurs due to?
failed fusion of the left or right maxillary prominence with the intermaxillary segment in early gestation.
Cleft palate occurs primarily when the palatine shelves fail to fuse. Cleft lip and palate can occur together or in isolation
How does neuropathy of the ilioinguinal nerve presents?
Presents with pain and allodynia in the anterior scrotum (labia majora in women), base of the penis (mons pubis), and medial thigh.
What can be used during stress testing to provoke areas of ischemic myocardium?
Stable angina results from fixed coronary artery stenosis that limits blood flow to downstream myocardium, preventing the myocardial oxygen supply from increasing during exertion.
Dobutamine mimics the effects of exercise and increases myocardial oxygen demand; it can be used during stress testing to provoke areas of ischemic myocardium, which can be recognized on imaging by a localized and transient decrease in contractility (ie, wall motion defect)
What is acute allergic contact dermatitis?
ACD, caused by a type IV (delayed) HSR to an antigen on the skin surface, typically presents with pruritic, erythematous, papulovesicular, weeping lesions.
Microscopically, acute ACD is characterized by spongiosis (ie, accumulation of fluid between keratinocytes in the epidermis)
What is intrapleural pressure at resting equilibrium?
The lungs generate a collapsing force and the chest wall generates an expanding force; the point at which these opposing forces are equivalent is the resting equilibrium of the respiratory system where alveolar pressure is equal to atmospheric pressure (ie, 0 cm H2O) and lung volume is the functional residual capacity.
The opposing forces create negative intrapleural pressure throughout the respiratory cycle; intrapleural pressure at resting equilibrium (ie, end-tidal expiration) is approximately -5 cm H2O.
What is lichen planus? Histopath?
Lichen planus presents with pruritic, purple/pink, polygonal papules and plaques that can affect the flexural surfaces of the wrists and ankles, along with the nails, oral mucous membranes, and genitalia.
histopath: hyperkeratosis (thickened stratum corner), bandlike lymphocytic infiltrate at the dermoepidermal junction, hypergranulosis (thickened granular layer), sawtooth rete ridges, and scattered eosinophilic colloid bodies
What is reactive arthritis?
Classic triad of reactive arthritis is nongonococcal urethritis, conjunctivitis, and arthritis.
It is an HLA-B27 associated arthropathy that occurs within several weeks following a genitourinary or enteric infection.
It belongs to the group of seronegative spondyloarthropathies (including ankylosing spondylitis) and can cause sacroiliitis in about 20% of cases.
Pauci-immune rapidly progressive glomerulonephritis frequently occurs as a manifestation of?
antineutrophil cytoplasmic antibodies (ANCA) associated vasculitides (eg, granulomatosis with polyangiitis, microscopic polyangiitis)
It is characterized by glomerular crescent formation without immunoglobulin or complement deposits.
What is the principal muscle of inspiration?
The diaphragm; innervated by the phrenic nerve (C3-5).
Although expiration is largely achieved through passive recoil, active expiration is aided by the internal intercostals (innervated by thoracic nerve rootlets) and abdominal muscles (innervated by thoracic and lumbar nerve roots)
Staphylococcal foodborne illness is due to?
the consumption of a preformed enterotoxin in contaminated food.
Most cases can be prevented by washing hands thoroughly prior to food preparation (prevents contamination) and ensuring proper refrigerated storage (prevents bacterial proliferation/enterotoxin production)
Chronic lymphocytic leukemia is a/w overexpression of?
BCL-2, an anti-apoptotic protein, on the mitochondrial membrane.
Treatment with a BCL inhibitors causes cancer cell death by promoting cytochrome c release from the mitochondria, which subsequently activates caspases.
What type of HSR is myasthenia gravis?
Myasthenia gravis results from an autoimmune type II (antibody mediated) HSR against skeletal myocyte surface acetylcholine receptors.
Goodpasture syndrome similarly involves autoantibodies against basement membrane collagen in the renal glomeruli and lung alveoli
What is dermatomyositis?
characterized by proximal muscle weakness (similar to polymyositis) and dermal manifestations (eg, heliotrope rash, Gottron papules).
Lab testing shows elevated muscle enzymes (eg, creatine kinase) and autoantibodies (eg, antinuclear, anti-Jo-1)
Initial treatment includes systemic glucocorticoids and evaluation for potential underlying malignancy
MOA of sulfonylureas (glyburide, glipizide)
Sulfonylureas inhibit the ATP-sensitive potassium channel on the pancreatic beta cell membrane, inducing depolarization and L-type calcium channel opening.
The increased Ca2+ influx stimulates beta cell insulin release independent of blood glucose concentrations, increasing the risk of hypoglycemia when meals are missed or during exercise
What is telomerase?
Critical shortening in telomere length can signal for programmed cell death.
Telomerase is a reverse transcriptase (RNA dependent DNA polymerase) that lengthens telomeres by adding TTAGGG repeats to the 3’ end of chromosomes.
Stem cells have long telomeres due to high telomerase activity, allowing them to proliferate indefinitely in a controlled manner.
Major histocompatobility complex (MHC) class II molecules are encoded by?
HLA-DP, HLA-DQ, and HLA-DR genes and present extracellular antigens processed in acidified lysosomes by antigen-presenting cells (eg, B cells, macrophages)
Absence of MHC class II expression impairs activation of B and T cells, resulting in a form of severe combined immunodeficiency
In patients with essential fructosuria, some of the dietary fructose load is converted by?
Essential fructosuria is a benign disorder of fructose metabolism caused by fructokinase deficiency.
In patients with essential fructosuria, some of the dietary fructose load is converted by hexokinase to fructose-6-phosphate, which can then enter glycolysis; this pathway is not significant in normal individuals
Indication of alveolar hemosiderin-laden macrophages
indicates alveolar hemorrhage.
They most commonly result from chronic elevation of pulmonary capillary hydrostatic pressure in the setting of left-sided heart failure.
What is an ependymomas?
Ependymomas orginate from the ependymal cells that line the ventricular system and the central canal of the spinal cord.
Ventricular ependymomas can block the flow of cerebrospinal fluid through the interventricular foramina, causing signs of increased intracranial pressure (eg, headache, papilledema) due to obstructive (noncommunicating) hydrocephalus
What is the relation of prevalence on positive predictive and negative predictive values?
As disease prevalence increases, the positive predictive values increases, and the negative predictive value decreases.
Traits of hep D virus
replication-defective RNA virus that is capable of causing infection only in the setting of coinfection with hep B. HBV provides hep B surface antigen for the HDV envelope
What is the primary virulence factor of strep pneumo?
polysaccharide capsule that inhibits opsonization and phagocytosis. The polysaccharide capsule of the most virulent strains is targeted by the pneumococcal vaccine, which confers immunity against those subtypes
Wilson disease is caused by?
defective copper transport within hepatocytes, which leads to impaired biliary excretion of copper. Hepatic copper accumulation eventually results in the release of free copper into the bloodstream and copper deposition into extrahepatic tissues (eg, basal ganglia, cornea)
