NBME 25 QUESTIONS AND ANSWERS 100% PASS

NBME 25 QUESTIONS AND ANSWERS 100% PASS Patient had anaphylaxis following the transfusion of fresh frozen plasma. What is the genetic deficiency? IgA deficiency. Patient with this disease may have preformed antibodies against IgA How does sitagliptin work? It is a competitive inhibitor of dipeptidyl peptidase-4 (DPP4). It prevents breakdown of GI incretins (ex: glucagon-like peptide, GLP-1) and promote endogenous release of insulin. ** DPP4 inhibitor increases endogenous insulin What are acoustic neuromas? Vestibular schwannoma Benign tumors of Schwann cells that arise from the vestibulocochlear nerve (CN VIII). How does acoustic neuromas cause symptoms? Lesions of CN VIII leads to ipsilateral hearing loss and positional dizziness Compression of the cerebellar peduncles leads to ipsilateral dysmetria What is the classic presentation of pyloric stenosis? Male infant 3-6 weeks of age with repeated vomiting after feeds, dehydration, and hypochloremic, hypokalemic metabolic alkalosis Explain the electrolyte and metabolic derangement seen with pyloric stenosis Vomiting - Hypochloremia Hypovolemia + excess bicarb - RAAS activation - increase renal tubule bicarb reabsorption - Metabolic alkalosis Metabolic alkalosis + hypovolemia + increased aldosterone - renal potassium excretion - hypokalemia How does hypokalemia worsens metabolic alkalosis? Hypokalemia further worsens metabolic alkalosis via trans-cellular exchange or extracellular sodium and protons in for potassium ions IV drug user presents with tricuspid regurgitation and signs and symptoms of right-sided heart failure. Diagnosis? Tricuspid valve endocarditis Tricuspid valve endocarditis is associated with what organisms? Staph Aureus Pseudomonas Candida Describe the sound and location of tricuspid regurgitation murmur? Holosystolic murmur best heard at the left lower sternal border What is the treatment for herpes simplex virus and varicella zoster virus? Guanosine analogs such as acyclovir, famciclovir, valacyclovir How does acyclovir, famciclovir, and valacyclovir work? Inhibits viral DNA polymerase First, they are phosphorylated by the viral thymidine kinase. Then, they are able to inhibit viral DNA polymerase by terminating the nascent DNA chain during replication. How does HSV or VZV confer resistance to guanosine analogs? Mutation in the viral thymidine kinase enzyme Guanosine analog would not be phosphorylated and thus cannot inhibit viral DNA polymerase. How does lithium carbonate cause nephrogenic diabetes insipidus? Lithium concentrates in the renal collecting duct, which then interferes with the signaling pathway of ADH Inhibits c-AMP-mediated pathway in the renal collecting duct What is the pathophysiology of nephrogenic diabetes insipidus? Renal collecting duct becomes insensitive to ADH. How does antidiuretic hormone work? ADH is released by the posterior pituitary in response to hypovolemia. It increases aquaporin channels in the cortical collecting duct via a c-AMP mediated pathway. This then reclaims free water - increase volume and decrease serum osmolality. What are lab findings associated with nephrogenic diabetes insipidus? Increased serum osmolarity Hypernatremia Inappropritely dilute urine How can nephrogenic DI be differentiated from central DI? Desmopressin (ADH analog) Nephorgenic DI - No response Central DI