Diagnosis of mast cell activation syndrome: a global consensus-2

The concept that disease rooted principally in chronic aberrant constitutive and reactive activation of mast cells (MCs), without the gross MC neoplasia in mastocytosis, first emerged in the 1980s, but only in the last decade has recognition of mast cell activation syndrome (MCAS) grown significantly. Two principal proposals for diagnostic criteria have emerged. One, originally published in 2012, is labeled by its authors as a consensus (re-termed here as consensus-1). Another sizable contingent of investigators and practitioners favor a different approach (originally published in 2011, newly termed here as consensus-2), resembling consensus-1 in some respects but differing in others, leading to substantial differences between these proposals in the numbers of patients qualifying for diagnosis (and thus treatment). Overdiagnosis by consensus-2 criteria has potential to be problematic, but underdiagnosis by consensus-1 criteria seems the far larger problem given (1) increasing appreciation that MCAS is prevalent (up to 17% of the general population), and (2) most MCAS patients, (r)egardless of illness duration prior to diagnosis, can eventually identify treatment yielding sustained improvement. We analyze these proposals (and others) and suggest that, until careful research provides more definitive answers, diagnosis by either proposal is valid, reasonable, and helpful.

Automated summary

In the past decade, recognition of mast cell activation syndrome (MCAS) has significantly increased, leading to two different proposals for diagnostic criteria. Consensus-1 and Consensus-2 are similar in some aspects but differ significantly in patient diagnosis. Therefore, accurately diagnosing MCAS remains a challenge.