title: Biphasic rattlesnake venom-induced thrombocytopenia.
abstract: 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.
authors.affiliation: Division of Medical Toxicology, San Diego Regional Poison Center, University of California-San Diego, 200 West Arbor Drive #8925, San Diego, CA 92103-8925, USA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Offerman
authors.forename: J David
authors.initials: JD
authors.lastname: Barry
authors.forename: Aaron
authors.initials: A
authors.lastname: Schneir
authors.forename: Richard F
authors.initials: RF
authors.lastname: Clark
mesh_terms: D000328:Adult; D000997:Antivenins; D003435:Crotalid Venoms / Q000009:adverse effects; D006801:Humans; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments / Q000627:therapeutic use*; D008297:Male; D012909:Snake Bites / Q000150:complications* / Q000188:drug therapy*; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000209:etiology*; D017211:Treatment Failure
chemical_list: D000997:Antivenins; D003435:Crotalid Venoms; C431183:Crotalidae Polyvalent immune Fab; D007140:Immunoglobulin Fab Fragments; D007128:Immunoglobulin Fragments