Mast cell activation syndrome: Proposed diagnostic criteria

Abstract

The term mast cell activation syndrome (MCAS) is finding increasing use as a diagnosis for subjects who present with signs and symptoms involving the dermis, gastrointestinal track, and cardiovascular system frequently accompanied by neurologic complaints. Such patients often have undergone multiple extensive medical evaluations by different physicians in varied disciplines without a definitive medical diagnosis until the diagnosis of MCAS is applied. However, MCAS as a distinct clinical entity has not been generally accepted, nor do there exist definitive criteria for diagnosis. Based on current understanding of this disease "syndrome" and on what we do know about mast cell activation and resulting pathology, we will explore and propose criteria for its diagnosis. The proposed criteria will be discussed in the context of other disorders involving mast cells or with similar presentations and as a basis for further scientific study and validation.

Figure 1

Bone marrow findings in patients with mast cell activation disorders. In panel A, tryptase-stained bone marrow sections revealed diffusely scattered spindle-shaped mast cells that did not form compact aggregates. In panel B, small-sized multifocal aggregates of mast cells were found, some of which contained 15 mast cells. Mast cells expressed CD25. Findings in panel A are consistent with the diagnosis of a monoclonal mast cell activation syndrome (MMAS), whereas findings in panel B are consistent with the diagnosis of systemic mastocytosis.