Other mast cell activation disorder

This code describes a group of rare, heterogeneous conditions characterized by the inappropriate and excessive release of mast cell mediators, leading to a wide range of symptoms affecting multiple organ systems. It encompasses mast cell activation disorders that do not meet the diagnostic criteria for systemic mastocytosis or other specified mast cell disorders.

Use this code for patients presenting with recurrent, multisystemic symptoms such as flushing, urticaria, angioedema, gastrointestinal issues, cardiovascular symptoms, and neuropsychiatric complaints, where laboratory findings (e.g., elevated tryptase, histamine metabolites) confirm mast cell activation but a definitive diagnosis of systemic mastocytosis or another specific mast cell disorder has been ruled out. Documentation should clearly indicate a diagnosis of "other mast cell activation disorder" or similar terminology.

• Ensure documentation explicitly states "other mast cell activation disorder" or a similar unspecified mast cell activation syndrome after ruling out more specific diagnoses.
• Do not confuse with D89.40 (Mast cell activation syndrome, unspecified) or D89.41 (Monoclonal mast cell activation syndrome).
• Code any associated symptoms or manifestations separately as secondary diagnoses.