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NBME 22 Answers

nbme22/Block 3/Question#40

A 49-year-old man has had the gradual onset of ...

Essential thrombocythemia

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submitted by link981(36),

Per First Aid 2018 (pg 421) & Merck Manual

a) CML is not the answer because in CML you have HIGH WBCs & Platelets. In the stem there is only high platelets. b) Is the answer because in Essential Thrombocythemia we have normal WBCs and RBCs, just high platelets. c) Myeloid metaplasia refers to well a metaplasia in myeloid cells which are basophils, eosinophils, etc. d) In Polycythemia Vera we have HIGH RBCs, WBCs, and Platelets. e) Reactive thrombocytosis- is a elevated platelet count that occurs secondary to another disorder like:

-Chronic inflammatory disorders (eg, rheumatoid arthritis, inflammatory bowel disease, tuberculosis, sarcoidosis, granulomatosis with polyangiitis) -Acute infection


-Iron deficiency



-Splenectomy or hyposplenism

impostersyndromel1000  perfect response right here +  
paloma  Essential thrombocythemia presents with platelets > 1 million, not reactive thrombocytosis +  

 +1  upvote downvote
submitted by bubbles(31),

Take a look at that massive platelet count -- over a million per mm3! That should point you towards a myeloproliferative disorder of some sort since this fella isn't bleeding out as far as we can tell from the blood panel (which would put reactive thrombocytosis on the ddx).

Now let's look at those erythrocytes. Normal -- so it's not polycythemia vera, and considering the lack of leukocytosis, probably not CML or myeloid metaplasia.

So our answer must be essential thrombocythemia!

FA 2017: Characterized by massive proliferation of megakaryocytes and platelets. Symptoms include bleeding and thrombosis. Blood smear shows markedly increased number of platelets, which may be large or otherwise abnormally formed. Erythromelalgia may occur.