Thrombocytopenia is a common occurrence in moderate to severe crotaline envenomation. The exact mechanism by which
rattlesnake venom leads to
thrombocytopenia is unclear, but aggressive treatment with crotaline-specific
antivenom often leads to resolution of this disorder. Crotalinae Polyvalent Immune Fab (
CroFab(TM), Protherics Inc., Nashville, TN) (crotaline Fab) is now available for the treatment of symptomatic rattlesnake envenomation. Although recurrence of
thrombocytopenia has been reported in patients after envenomation treated with crotaline Fab, cases refractory to this
therapy have not been described. We report a case of severe crotaline envenomation that appears to have exhibited two separate episodes of
thrombocytopenia, only one of which responded to
antivenom. The second, later phase was refractory to both crotaline Fab as well as traditional
Antivenin (Crotalinae) Polyvalent (Wyeth-Ayerst
Pharmaceuticals, Philadelphia, PA) (ACP). By reviewing the literature regarding
venom-induced
thrombocytopenia, we attempt to explain this "biphasic" phenomenon and the inability of crotaline Fab to reverse this toxic effect.