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NBME 20 Answers

nbme20/Block 2/Question#17

A 57-year old man has a hemoglobin concentration of ...

Chronic obstructive pulmonary disease

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 +9  upvote downvote
submitted by hayayah(599),

This is reactive polycythemia vera, which is due to high altitude or lung disease. SaO2 is low, and EPO is increased.

Another way to approach the question is looking at the blood smear. It's pretty normal (no megakaryocytes, no increased number of platelets, no rods, nothing blue, etc). A blood smear from a COPD patient will be normal. Just an increased number of RBCs due to the increased EPO leading to increased Hgb.

mbourne  You shouldn't call it reactive polycythemia "vera", as polycythemia vera is a seperate disease with entirely different etiology. This is Reactive Polycythemia, or as another poster said, appropriate absolute polycythemia secondary to chronic hypoxia. +5  

 +3  upvote downvote
submitted by alexb(31),

I confused myelodysplastic syndrome with primary myelofibrosis because I thought 2-3 of those RBCs looked like teardrop cells. Just like when they show an image for bullous pemphigoid and there's some weird second rip through the dermal/subdermal layer making me think it's not BP even though I don't know what else it would be. fml

whoissaad  Made the same mistake +3  
targetusmle  i thought exactly the same!! 2 cells looked like tear drop cells :/ +2  
ilovemypuppies2295  I thought there were tear drop cells too. Seemed like it should be a metaplasia then. Oh well +  
lynn  I did the same, but looking at FA19 pg 423 it says "ineffective hematopoiesis --> defects in cell maturation of nonlymphoid lineage." You can get bilobed neutrophils, or if it progressed to AML you'd see auer rods. Nothing about tear drop cells. Then on pg 406 tear drop cells would be seen in myelofibrosis, and possibly thalassemias +  

Pt has polycythemia vera (myeloproliferative disorder) due to chronic hypoxia induced by COPD. Myeloid metaplasia is extra medullary hematopoiesis due to myelofibrosis. Hereditary hemochromatosis would have been proven by a prussian blue stain. Hypersplenism would have caused decreased RBCs, and myelodysplasic syndrome would have shown Auer rods or blasts.

neonem  Right, I think this would be just called "appropriate absolute polycythemia", whereas polycythemia vera is due to a malignant JAK2 mutation and would be termed a type of chronic myeloproliferative disorder. +9