Thrombotic microangiopathies

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HUS/TTP, antiphospholipid syndrome, malignant HT., systemic sclerosis (renal crisis), HIV, pregnancy (preeclampsia, HELLP: hemolysis, elevated liver enzymes, low platelet count), hematopoietic stem cell transplantation
Pentad: thrombocytopenic purpura, intravascular hemolytic anemia (fragmented RBCs), fever, + AKI (HUS), + neurol. dis. (TTP)
Drugs: mitomycin, gemcitabine, VEGF inh., anti-rejection (calcineurin inhibitors, OKT3), pills, antiplatelets (ticlopidine, clopidogrel, prasugrel), quinine
PT, aPTT: normal
Interlobular artery, arterioles, glomerular capillaries: microthrombi, AKI
DD: DIC, SLE, cancer
TTP and HUS: ADAMTS13 metalloprotease (which cleaves von Willebrand's factor) deficiency, hypocomplementemia
TTP (thrombotic thrombocytopenic purpura)
- Familial, acquired, sporadic
- Rx: Plasmapheresis, Rituximab (CD20 Ab to deplete B cell), steroids
HUS (hemolytic-uremic syndrome):
- (esp. children) Shiga toxin [verotoxin] with enterohemorrhagic diarrhea (STEC: E. coli O157:H7, rarely Shigella), pneumococcus (rare), supportive Rx (no antibiotics, no anti-diarrhea Rx), dialysis prn.
- (children or adults) Atypical HUS (complement activation): very rare, genetic or acquired, no diarrhea, normal or partial def. ADAMTS13
- Rx: Plasmapheresis (not for typical STEC HUS), eculizumab (C5 Ab) for atypical HUS, (splenectomy)