Systemic mastocytosis is a disorder that results in an excessive number of mast cells in your body. Mast cells normally help protect you from disease and aid in wound healing by releasing substances such as histamine and leukotrienes.

But if you have systemic mastocytosis, excess mast cells generally build up in your skin, bone marrow, gastrointestinal tract and bones. When triggered, these mast cells release substances that can overwhelm your body and result in signs and symptoms such as facial flushing, itching, a rapid heartbeat, abdominal cramps, lightheadedness or even loss of consciousness. Common triggers include alcohol, temperature changes, spicy foods and certain medications.

Several types of systemic mastocytosis exist. The most common form — indolent systemic mastocytosis — progresses slowly.

The second most common form is systemic mastocytosis associated with a second blood disorder. Another type, aggressive systemic mastocytosis, develops rapidly and is often associated with organ damage. Mast cell leukemia and mast cell sarcoma are extremely rare forms of systemic mastocytosis.