Deck XVIII Flashcards Preview

USMLE World Missed Questions > Deck XVIII > Flashcards

Flashcards in Deck XVIII Deck (30):

What antineoplastic drug is an adenosine analog and reaches high intracellular concentrations due to resistance to adenosine deaminase?



What is the drug of choice in hairy cell leukemia and what drug class is it in?

Cladribine, a purine analogue.


To what receptors does von Willebrand Factor bind?

GP Ib-IX receptors on the platelet membrane


What test is used to measure vWF platelet aggregation?

Addition of Ristocetin; this produces poor platelet aggregation in patients with a vWF deficiency.


What is the pharmacologic treatment for vWF deficiency?

Desmopressin (DDAVP) which stimulates vWF release from the endothelium.


In a patient who ingested rat poison, what must be administered to prevent life threatening GI bleeding?

Fresh frozen plasma- this restores the clotting factors II, VII, IX, and X (vitamin K dependent factors) which are depleted by the poison. Vitamin K should also be given.


Most anemias produce increased production of what blood parameter as a compensatory response?



What is the classic triad of symptoms in aplastic anemia?

Low hemoglobin, absent hematopoietic cells in the bone marrow, thrombocytopenia.


In what conditions is an increased reticulocyte index seen?

Hemolytic or hemorrhagic anemia assuming normal bone marrow function. In aplastic anemia, it is low because there are few marrow progenitor cells.


What is erythropoietin?

A hormone secreted by the kidneys to induce RBC formation.


What cell surface glycoprotein may prevent the action of chemotherapeutic agents?

The human multidrug resistance (MDR1) gene codes for P-glycoprotein which is a transmembrane ATP dependent efflux pump protein that has broad specificity for hydrophobic compounds. It can reduce drug influx into the cytosol and can increase drug efflux from the cytosol preventing action of chemotherapeutic agents.


What drug can be administered to reverse methotrexate toxicity?

Folinic acid (leucovorin)


What is the function of leucovorin?

To rescue bone marrow, gastrointestinal, and other mucosal cells from toxicity following high dose methotrexate administration.


What is a principle difference between Hepatitis C and Hepatitis B viruses?

Hep C is an RNA virus, Hep B is a DNA virus.


Describe the difference in Hep. B and Hep C. liver toxicity.

Hepatitis B virus integrates its DNA into the host genome which increases risk for HCC. Hepatitis C is an RNA virus and lacks reverse transcriptase so does not integrate into the host genome.


In patients with B12 deficiency, what is the most common means of supplement administration?

Parenterally; oral supplementation only corrects the deficiency in patients with insufficient intake. For most patients (with gastric atrophy, intrinsic factor deficiency, or terminal illeal disease), parenteral administration is required.


Patients with repeated blood transfusions are likely to have buildup of what substance? And what form is this deposited in?

Iron buildup. Deposited as hemosiderin within tissues.


What symptoms are characteristic of paroxysmal nocturnal hemoglobinuria (PNH)?

Hemolytic anemia, hypercoaguability, pancytopenia.


What genetic mutation is associated with paroxysmal nocturnal hemoglobinuria?

Aquired PIGA gene mutation within a clonal population of multipotent hematopoietic stem cells. The gene is involved in glycosylphosphatidylinositol anchor (GPI) synthesis which is necessary for attachment of cell surface proteins including CD55 and CD59.


What is the function of CD55?

Decay accelerating factor.


What is the function of CD59?

MAC inhibitory protein.


What deficiencies are present in patients with paroxysmal nocturnal hemoglobinuria?

CD55 and CD59 deficiency and deficiency in complement-mediated hemolysis.


What complications are associated with paroxysmal nocturnal hemoglobinuria?

Budd chiari syndrome due to thrombotic complications, pancytopenia, aplastic anemia.


How is Paroxysmal Nocturnal Hemoglobinuria diagnosed?

Flow cytometry will show absence of GPI anchor and CD55 and CD59 deficiency.


Where are most coagulation factors synthesized?

In the liver.


What coagulation factor has the shortest half life?

Factor VII, part of the extrinsic pathway.


What coagulation factor is most likely to first become deficient in a patient with liver failure and what lab result will reflect this deficiency?

Factor VII deficiency resulting in prolonged PT.


What lab value must be monitored in a patient taking warfarin?

PT (or INR).


What is used to most rapidly reverse warfarin toxicity?

Fresh frozen plasma.


What is implicated by presence of erythroid precursor cells in the liver and spleen?

Extramedullary hematopoiesis