Colonic biopsy in verotoxin-induced hemorrhagic colitis and thrombotic thrombocytopenic purpura (TTP).

Sporadic cases and occasional outbreaks of hemorrhagic colitis recently have been associated with the rare Escherichia coli serotype O157:H7, which is now recognized as an important identifiable cause of bloody diarrhea in patients in whom more common gut pathogens cannot be detected. The authors report such a case in a 49-year-old woman who developed thrombotic thrombocytopenic purpura (TTP) and hemorrhagic transverse and descending colitis with a lesion having many of the features of pseudomembranous colitis. While pseudomembrane formation has been described in the hemolytic uremic syndrome (HUS), these features have not, to the authors' knowledge, been described in a patient with hemorrhagic colitis and TTP secondary to a verotoxin-producing serotype of E. coli.