Master the board step 3

Master the Boards: USMLE Step 3
Get an ADAMTS-13 level in
TTP/HUS.
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TTP pentad (FAT RN) also has the following
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Fever (F: Fever)
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Neurological abnormalities (N: Neurological issues)
ADAMTS-13 level is down in TTP.
Treatment
Some cases resolve on their own. Severe cases of either TTP or HUS should
be treated with plasmapheresis. Steroids will not help. Antibiotics for HUS
from E. coli may make it worse; platelet transfusions for either will definitely
make it worse.
Basic Science Correlate
Mechanism of HUS/TTP
ADAMTS-13 is the metalloproteinase that breaks down von Willebrand’s
factor (VWF) to release platelets from one another. When VWF is not
dissolved, the platelets form abnormally prolonged strands that serve as
a barrier to RBCs. RBCs that run into these strands break down and are
destroyed. The purpose of plasmapheresis in the treatment of severe TTP is
to replace the ADAMTS-13. This is why giving platelets only makes matters
worse: It increases the size of the abnormal platelet strands.
Eculizumab inhibits C-5
and prevents complement
activation. PNH is treated
with eculizumab.
Paroxysmal Nocturnal Hemoglobinuria (PNH)
Presents with pancytopenia and recurrent episodes of dark urine, particularly
in the morning. The most common cause of death is large vessel venous
thrombosis, such as portal vein thrombosis.
PNH can transform into the following:
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Aplastic anemia
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Acute myelogenous leukemia (AML)
Diagnostic Testing
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Most accurate test: CD 55 and CD 59 antibody (also known as decay accelerating
factor)
Treatment
The best initial treatment is with glucocorticoids, such as prednisone.
Transfusion-dependent patients with severe illness are treated with eculizumab.
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