Autoimmune Heparin-Induced Thrombocytopenia (aHIT)

Features:

(1) clinical and laboratory features of heparin-induced thrombocytopenia

(2) anti-platelet factor 4 (anti-PF4) polyanion antibodies

(3) heparin-independent platelet activation

Syndromes that may occur with aHIT:

(1) spontaneous HIT (onset without previous heparin exposure)

(2) flush heparin HIT (HIT after exposure to a heparin flush)

(3) delayed-onset HIT (HIT begins or worsens after stopping heparin)

(4) persisting HIT (HIT that continues for > 1 week after stopping heparin)

(5) fondaparinux-associated HIT

(6) severe HIT with overt DIC with hypofibrinogenemia and microvascular thrombosis