Systemic mastocytosis: A concise clinical and laboratory review

Context. - Systemic mastocytosis is characterized by abnormal growth and accumulation of neoplastic mast cells in various organs. The clinical presentation is varied and may include skin rash, symptoms related to release of mast cell mediators, and/or organopathy from involvement of bone, liver, spleen, bowel, or bone marrow. Objective. - To concisely review pathogenesis, disease classification, clinical features, diagnosis, and treatment of mast cell disorders. Data Sources. - Pertinent literature emerging during the last 20 years in the field of mast cell disorders. Conclusions. - The cornerstone of diagnosis is careful bone marrow histologic examination with appropriate immunohistochemical studies. Ancillary tests such as mast cell immunophenotyping, cytogenetic/molecular studies, and serum tryptase levels assist in confirming the diagnosis. Patients with cutaneous disease or with low systemic mast cell burden are generally managed symptomatically. In the patients requiring mast cell cytoreductive therapy, treatment decisions are increasingly being guided by results of molecular studies. Most patients carry the kit D816V mutation and are predicted to be resistant to imatinib mesylate (Gleevec) therapy. In contrast, patients carrying the FIP1L1-PDGFRA mutation achieve complete responses with low-dose imatinib therapy. Other therapeutic options include use of interferon-α, chemotherapy (2-chlorodeoxyadenosine), or novel small molecule tyrosine kinase inhibitors currently in clinical trials.