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NBME 19 Answers

nbme19/Block 3/Question#50 (8.5 difficulty score)
39 yo man, 6 months of headache, muscle ...
Basophilic stipplingπŸ”
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 +10 
submitted by cassdawg(959),

So I hate this question because you can know what the diagnosis is and still miss it.

TL;DR: This is lead poisioning, so there is basophilic stippling in a peripheral blood smear [BUT ringed sideroblasts would also be found in the bone marrow]

Why this is lead poisoning: (FA2020 p425)

  • Microcytic Anemia (caused by lead inhibition of ferrocheletase and ALA dehydratase)
  • Environmental exposure (ammunition at the range, he is an officer)
  • GI effects (crampy abdominal pain)
  • Neurological effects (headache, irritability, distractability, forgetful, motor weakness)

Why it is NOT the other answers:

  • Auer rods - characteristic of acute myelogenous leukemia which would present with pancytopenias (his WBCs are normal) along with circulating myeloblasts on peripheral smear; median age onset 65 years and he has no risk factors
  • Oval Macrocytes - in macrocytic anemias (B12 or folate deficiency), this is microcytic as indicated by MCV
  • Pleomorphic lymphocytes - occur in chronic lymphocytic leukemias and infectious mono, both which have different symptomotologies
  • Ringed sideroblasts - are from lead poisoning but are in the bone marrow
  • Scistocytes - characteristic RBC which has been through a clogged vessel and sheared off, found in microangiopathic hemolytic anemias (MAHAs) like thrombotic microangiopathies like TTP and HUS (typically normocytic anemia and different presentation; a question would likely give you more info on the thrombolytic pathway if they wanted you to choose this; we didn't even get a platelet count here)
  • Target Cells: found in HbC disease (glutamic acid to lysine in hemoglobin, causes extravascular hemolysis), liver disease, asplenia, and Thalassemia (deletions in either alpha or beta chain of hemaglobin, causes anemia that would be present from childhood and would not have neuro symptoms)
ftr_dr_bowowers  thank you! +1