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Abetalipoproteinemia is a condition where ApoB-48 and ApoB-100 production is deficient.
All you need to know about ApoB-48 is that it is the apolipoprotein responsible for allowing chylomicrons that are absorbed by the gut to be released into the circulation.
| Fat droplets in bowel wall on biopsy = abetalipoproteinemia. Weird/unusual detail that sounds extraneous and low-yield, but there’s a question floating around somewhere that shows large, clear droplets within enterocytes on biopsy, and the answer is abetalipoproteinemia. |
The other important point about abetalipoproteinemia is that it leads to acanthocytes (spur cells). These are spiky-looking RBCs. If they show you a blood smear of spiky RBCs and mention intestinal/absorptive problems in the vignette, the answer is abetalipoproteinemia.
| Spur cells are the USMLE giveaway for abetalipoproteinemia. |
Now for the greater value of this post (because many people reading this might already be aware of the association between abetalipoproteinemia and spur cells):
Acanthocytes are also seen in liver failure. Memorize that.
There’s a USMLE question that mentions an elderly woman found unconscious in her home on a hot summer day with hyperthermia. They say she has acanthocytes on blood smear and ask for the diagnosis. The answer is liver failure.
Heat stroke = end-organ damage secondary to increased body temperature.
Heat exhaustion = no end-organ damage and less severe than heat stroke.
If you reason that the old lady has heat stroke, then that explains why she has acanthocytes in her blood. It’s because she has end-organ failure (in this case, hepatic).
That’s it. Would you rather read a superfluous, 3000-word essay that doesn’t tell you exactly what you need to know.
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