Thrombotic thrombocytopenic purpura in southeastern New England

Eight patients with thrombotic thrombocytopenic purpura (TTP) originating within a 25-mile radius had their conditions diagnosed in a three-year period at a community teaching hospital in southeastern New England. In the preceding ten years, only one case of TTP had occurred in the same hospital. A niece-uncle relationship was present in two patients, and lymphocyte typing showed that they both shared an HLA haplotype. In the remaining patients, no social, familial, or environmental connection was established. Three patients died, all of whom were female. Six patients received exchange plasmapheresis with excellent responses in five. Autopsies in the three fatal cases showed widespread organ involvement with TTP but did not disclose evidence of any common underlying disease. This unusual occurrence should alert physicians to the possibility of localized outbreaks of TTP and the necessity of considering this diagnosis in all patients with unexplained thrombocytopenia.