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submitted by nala_ula(68),

The histology is of spherocytes (small spherical cells w/o central pallor). Hereditary spherocytosis is due to defect in proteins interacting with RBC membrane skeleton and plasma membrane (ankyrin, band 3, protein 4.2, spectrin). Mostly autosomal dominant inheritance (so heterozygous mutation since you only need one mutant allele to get the disease).

wuagbe  To add to this: homozygous HS presents with hemolysis even in absence of stressors. this patient is only presenting with pale skin, and there are no schistocytes on the peripheral smear, so it's a heterozygous ankyrin mutation. +3  
pg32  I wanted to pick hereditary spherocytosis but the mean corpuscular concentration was normal and I thought it was supposed to be elevated? Also, why are there so many RBCs that are way bigger than the spherocytes? +4  
nephroguy  I'm assuming that the MCC is normal because the patient is heterozygous for HS. Not sure if this is correct, but that was my thought process +1  
draykid  Are there any papers that explain the difference in expression of homozygous vs heterozygous HS? +1  
waterloo  I don't know if that matters as much, like the phenotype difference of homozygous or heterozygous for this question. Since you only need one allele to show this, play odds. Is he more likely to have AA or Aa. That was my thought process. Also if you see spherocytes you'd be going for ankyrin right, not B-globin bc that should be target cells - regardless of MCHC. +1  
alimd  as I remember AD are always heterzygous. Because homozygous are always lethal. +  


submitted by lilyo(34),

Prosthetic valves are one of the causes of extravascular hemolysis so suspect this in a patient that has symptoms of anemia such as fatigue, pallor, jaundice. Further supporting evidence in this patient is the increased indirect bilirubin. Also, look for elevated LDH, decreased haptoglobin.

nephroguy  All of this is correct except its intravascular hemolysis, not extravascular. Also look for hemosiderinuria, hemoglobinuria and schistocytes on blood smear +1  
dermgirl  Is not intravascular hemolysis, it is extrinsic hemolysis, specifically macroangiopathic hemolytic anemia. FA 2020 page 423. +  
vishnu_c_singh  This is actually BOTH intravascular hemolysis & extrinsic hemolysis. Extrinsic = hemolysis that isn't caused by an internal defect of the RBCs, like an enzyme/membrane defect (in other words, it's hemolysis due to an external factor like a mechanical valve). Intravascular = hemolysis that occurs within the blood vessels (RBCs get damaged as they pass through the valve). This is in contrast to extravascular hemolysis which describes hemolysis that occurs outside of the blood vessels (e.g. inside the spleen) +1  


submitted by xxabi(198),

I was under the impression that this was an aortic dissection, due to "severe chest pain" as well as the false lumen in the aorta. And HTN is the #1 risk factor for aortic dissection. Someone correct me if i'm wrong, but I think this is aortic dissection rather than aortic aneurysm.

chefcurry  I believe so, FA 2018 pg 299 +3  
ergogenic22  It is dissection "extra lumen in the media of the proximal aorta" = "a longitudinal intimal (tunica intima) tear with dissection of blood through the media of the aortic wall" ... answer is still hypertension +1  
breis  FA 2019: 301 +  
pg32  First Aid says that aortic dissection causes widening of the mediastinum and is due to an intimal tear, so I thought it wasn't an aortic dissection. Can anyone help me understand why First Aid was wrong in this case? Thanks! +3  
nephroguy  @pg32 The question stems states that there is no widening of the Aorta, not the mediastinum. Widening of the mediastinum is seen in dissection while widening of the aorta is seen in aneurysm. Also the intimal tear creates a false lumen between the intima and media. Hope that helps! +3  


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