UWorld Step 1 Qbank: Your world of learning. Subscribe now.

NBME 23 Answers

nbme23/Block 4/Question#24
A 60-year-old man comes to the physician ...
Erythropoietin🔍

Login to comment/vote.


Patient has polycythemia vera, as evidenced by erythrocytosis, granulocytosis, and headaches & diziness. EPO is decreased due to erythrocytosis. Decreased LAP would indicate CML, not PV.

btl_nyc  I thought this was CML. What am I missing that would say CML over PV? +2  
btl_nyc  Nvm, RBCs go down in CML, but everything goes up in PV. +7  
arcanumm  Tricked me. I knew right away that it was PV, but I thought PV would crowd out normal cell creation (e.g. decrease platelets). So apparently crowding out normal cells is just a quality of AML/CML? +  
drzed  More AML. Remember Sattar always stresses that all the myeloproliferative disorders are expansions of ALL lineages, ESPECIALLY "xx" (depends on which one, for CML it'll be granulocytes, for PV it'll be RBCs etc). They're called MYELOproliferative because all the myeloid linages go up, but one will be increased more than the rest. In this case, it is the RBCs. +1  



 +4  upvote downvote
submitted by guillo12(37),

"PV is a neoplastic (clonal) blood disorder with autonomous (EPO-independent) erythroid proliferation. Because of the existence of a negative feedback mechanism, the erthrocytosis in PV down-regulates EPO production and results in below normal serum EPO levels. In contrast, an EPO-driven erythrocytosis characterizes secondary erythrocytosis, and this condition may be associated with either high or normal serum EPO levels."

https://www.mayoclinicproceedings.org/article/S0025-6196(11)63840-8/fulltext

qball  For those that want to know what total red cell mass means in polycythemia and PV read the first paragraph in this article. The hemoglobin and hematocrit do NOT inform you of the total red cell mass. +  



Increased Levels of Myeloid cells ( Erythrocytosis, thrombocythemia, and granulocytosis) plus Dizziness and Headache increase the suspicion for Polycythemia vera.

Low EPO in PV due to Negative feedback on EPO release by kidney.

dentist  This is where the timing of everything in the question trips me up. FA say PV mechanism is increase EPO (2019, p299) +  
paulkarr  Different types of Polycythemia have different effects on EPO levels. "Appropriate Absolute" and "Inappropriate Absolute" will both increase EPO levels (Inappropriate is caused by this EPO increase). Where as Polycythemia Vera has decreased EPO levels due to the negative feedback loop. FA2019 pg 425 hooks it up nicely. +1  



Primary polycythemia = Disorder of Increased no of RBCs, usually due to acquired JAK2 mutation. May present as intense itching after shower (aquagenic pruritus). Rare but classic symptom is erythromelalgia (severe, burning pain and red-blue coloration) due to episodic blood clots in vessels of the extremities. There is DECREASED EPO (vs 2° polycythemia, which presents with endogenous or artificially raised EPO). Treatment: phlebotomy, hydroxyurea, ruxolitinib (JAK1/2 inhibitor).




UWorld Step 1 Qbank: Your world of learning. Subscribe now.