MCAS is an immunological condition in which mast cells inappropriately and excessively release chemical mediators, resulting in a range of chronic symptoms, sometimes including anaphylaxis or near-anaphylaxis attacks. Primary symptoms include cardiovascular, dermatological, gastrointestinal, neurological and respiratory problems.

With mast cell activation syndrome (MCAS), the mast cells in your body function abnormally. This leads to excessive allergic-like response with many potential causes, including genetic changes identified by the evolving research. MCAS can lead to a wide range of symptoms, including body-wide reactions, that can be difficult to diagnose.

Mast cell activation syndrome (MCAS) is a disorder in which mast cells release excessive inflammatory chemicals in response to a normally harmless trigger. People with MCAS can experience symptoms that affect the skin, gastrointestinal, respiratory, cardiovascular, musculoskeletal, neurological, and genitourinary systems.

Mast cell activation syndrome (MCAS) causes a person to have repeated severe allergy symptoms affecting several body systems. In MCAS, mast cells mistakenly release too many chemical agents, resulting in symptoms in the skin, gastrointestinal tract, heart, respiratory, and neurologic systems.

Mast cell activation syndrome is increased and inappropriate activation of mast cells without clonal proliferation. Symptoms result mainly from mediator release and include pruritus, flushing, and dyspepsia due to gastric hypersecretion. Diagnosis is by skin or bone marrow biopsy or both.