Interferon-Induced Thrombotic Microangiopathy

Interferon (IFN) is an effective therapy for multiple disorders. An infrequently reported side effect is thrombotic microangiopathy (TMA): thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). We published the first comprehensive review analyzing this association with the following observations: (1) there was a higher incidence of IFN-induced TMA in myeloproliferative disorders (chronic myelogenous leukemia (CML)) than that in nonmalignant disorders (multiple sclerosis (MS), chronic hepatitis C virus infection (HCV)); (2) mean age at diagnosis was 47 years; (3) there was rare association with hairy cell leukemia (HCL), Sezary syndrome (one case each) and no cases reported for polycythemia vera (PV); (4) sex distribution was balanced (exception of higher prevalence in females for MS); (5) TMA was insidious in onset with long incubation periods (average treatment duration 40.4 months); (6) comparative analysis of mean time (months) to onset of TMA ensuing cumulative IFN exposure was: MS 68.6 vs. CML 35.5 vs. HCV 30.4; (7) confirmed TTP (low ADAMTS 13 levels) was associated with the presence of an inhibitor; (8) outcome analysis revealed complete remission in 27 (40%), persistent chronic kidney disease in 28 (42%) and fatality in 12 patients (18%); (9) corticosteroids, plasma exchange (PEX) and rituximab are effective therapies.