Systemic mastocytosis (SM)

Systemic mastocytosis is a condition caused by the accumulation of mast cells in more than one part of the body. Mast cells contain substances such as histamine that regulate allergic reactions. In systemic mastocytosis, mast cells may build up in the bone marrow, internal organs, or in the skin. There are several different types of systemic mastocytosis. Indolent systemic mastocytosis develops slowly, while aggressive systemic mastocytosis develops more rapidly. Another form, called systemic mastocytosis with associated hemotologic non-mast cell lineage disease (SM-AHNMD), is characterized by the presence of several types of blood disorders. Mast cell leukemia is a rare form of systemic mastocytosis.