[Mastocytosis--two diseases with different physiopathology].

Mastocytosis means proliferation and accumulation of mast cells in skin and internal organs. Bone marrow cytogenetic abnormalities are similar to those found in myeloproliferative diseases. Recent findings indicate different pathogenetic forms of mastocytosis. Thus, adult patients with associated hematological diseases express mutation of the gene for the thyrosine kinase receptor, while childhood cases lack this mutation. In adults the skin and bone marrow are the most commonly affected organs but involvement of the skeleton and gastrointestinal tract also occur. Hematological malignancy is a rare but well-recognized complication. Childhood onset mastocytosis in the skin regresses spontaneously, whereas virtually all of the adult-onset cases persist.