M astocytosisisadisordercharacterizedbymastcell accumulation in tissue most commonly in the skin, and it may also affect the bone marrow, gastrointestinal tract, skeletal system, liver, spleen, and lymph nodes. A World Health Organization consensus group 1 recently divided the disease into 7 forms: cutaneous mastocytosis, indolent systemic mastocytosis, systemic mastocytosis with an associated hematologic non-mast cell lineage, aggressive systemic mastocytosis, mast cell leukemia, mast cell sarcoma, and extracutaneous mastocytoma. Systemic mastocytosis is mostly an adult phenomenon.