Thrombotic thrombocytopenic purpura in a patient with interferon treated hepatitis C successfully treated with rituximab

Drug‐induced thrombotic thrombocytopenic purpura: A systematic review and review of European and North American pharmacovigilance data

Many medications have been reported to be associated with thrombotic thrombocytopenic purpura (TTP) through pharmacovigilance data and published case reports. Whilst there are existing data available regarding drug-induced thrombotic microangiopathy, there is no available synthesis of evidence to assess drug-induced TTP (DI-TTP). Despite this lack of evidence, patients with TTP are often advised against using many medications due to the theoretical risk of DI-TTP. This systematic review evaluated the evidence for an association of medications reported as potential triggers for TTP. Of 5098 records available 261 articles were assessed further for eligibility. Fifty-seven reports, totalling 90 patients, were included in the final analysis. There were no cases where the level of association was rated as definite or probable, demonstrating a lack of evidence of any drug causing DI-TTP. This paucity of evidence was also demonstrated in the pharmacovigilance data, where 613 drugs were reported as potential causes of TTP without assessment of the strength of association. This systematic review demonstrates the need for standardised reporting of potential drugs causing TTP. Many reports omit basic information and, therefore, hinder the chance of finding a causative link if one exists.

Emerging Concepts in Immune Thrombotic Thrombocytopenic Purpura

Immune thrombotic thrombocytopenic purpura (iTTP) is an autoimmune disorder of which the etiology is not fully understood. Autoantibodies targeting ADAMTS13 in iTTP patients have extensively been studied, the immunological mechanisms leading to the breach of tolerance remain to be uncovered. This review addresses the current knowledge on genetic factors associated with the development of iTTP and the interplay between the patient's immune system and environmental factors in the induction of autoimmunity against ADAMTS13. HLA-DRB1*11 has been identified as a risk factor for iTTP in the Caucasian population. Interestingly, HLA-DRB1*08:03 was recently identified as a risk factor in the Japanese population. Combined in vitro and in silico MHC class II peptide presentation approaches suggest that an ADAMTS13-derived peptide may bind to both HLA-DRB1*11 and HLA-DRB1*08:03 through different anchor-residues. It is apparent that iTTP is associated with the presence of infectious microorganisms, viruses being the most widely associated with development of iTTP. Infections may potentially lead to loss of tolerance resulting in the shift from immune homeostasis to autoimmunity. In the model we propose in this review, infections disrupt the epithelial barriers in the gut or lung, promoting exposure of antigen presenting cells in the mucosa-associated lymphoid tissue to the microorganisms. This may result in breach of tolerance through the presentation of microorganism-derived peptides that are homologous to ADAMTS13 on risk alleles for iTTP.

Interferon induced thrombotic microangiopathy (TMA): Analysis and concise review

Interferon (IFN) has been associated with development of thrombotic microangiopathy including thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). We reviewed literature from the earliest reported association in 1993, to July 2016 and found 68 cases. Analysis of this data shows: (1) Mean age at diagnosis was 47 years (95% CI, 44-50). (2) Majority of cases were seen where IFN was used for the treatment of chronic myelogenous leukemia (CML), multiple sclerosis (MS), chronic hepatitis C virus infection (HCV) and one case each for hairy cell leukemia (HCL) and Sezary syndrome. (3) There were no cases reported for polycythemia vera (PV) or lymphoma. (4) Sex distribution was nearly equivalent with the exception in patients with multiple sclerosis where there was female predominance (12 of 16 with reported data). (5) For pooled analysis, the average duration of treatment with IFN before TMA was diagnosed was 40.4 months. (6) Comparative analysis showed that patients with MS required the highest cumulative dose exposure before developing TMA (MS 68.6 months, CML 35.5 months, HCV 30.4 months). (7) Cases of confirmed TTP (where A disintegrin and Metalloprotease with thrombospondin type 1 motif 13: ADAMTS 13 level was measured) showed presence of an inhibitor. (8) In all cases of confirmed TTP, moderate to severe thrombocytopenia was a striking clinical feature at presentation while this was not a consistent finding in all other cases of TMA. (9) Outcome analysis revealed complete remission in 27 (40%), persistent chronic kidney disease (CKD) in 28 (42%) and fatality in 12 patients (18%). (10) Treatment with corticosteroids, plasma exchange and rituximab resulted in durable responses.