Systemic mastocytosis (mas-to-sy-TOE-sis) is a rare disorder caused by a mutation 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. But if you have systemic mastocytosis, excess mast cells can build up in various parts of your body.
When triggered, these mast cells release substances that can overwhelm your body. You might experience 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.
Systemic mastocytosis is classified into seven subtypes. The most common form progresses slowly, but there are others that develop rapidly. Mast cell leukemia and mast cell sarcoma subtypes are extremely rare forms of systemic mastocytosis.