Systemic Mastocytosis

The term mastocytosis encompasses a heterogeneous group of clonal diseases characterized by proliferation and accumulation of mast cells (MC) in different tissues, mainly skin and bone marrow (BM). Cutaneous mastocytosis (CM), typical in the childhood, is the most frequent form of mastocytosis, while systemic disease (SM) mainly affects adults and involves one or more extra-cutaneous organs (BM, gastrointestinal tract, lymph nods and spleen), with or without skin involvement. The majority of cases of SM show a somatic ‘autoactivating’ point mutation at codon 816 of kit-receptor gene. Mastocytosis has a wide variety of clinical manifestations due to the inappropriate release of mediators by MCs (e.g. pruritus, urticaria, angioedema, flushing, nausea, vomiting, abdominal pain, diarrhea, episodic anaphylactoid attacks, osteopenia/osteoporosis) and to skin disease (urticaria pigmentosa); in the rare cases of aggressive disease, the clinical features are related to organ dysfunction from MC tissue infiltration (e.g. hypersplenism, patho- logic bone fractures, ascites, malabsorption, cytopenias).