Clinical Approach to Mast Cell Activation Syndromes: A Practical Overview.

The diagnosis of mast cell activation syndromes (MCAS) is defined by 3 criteria: 1) typical clinical signs and symptoms of acute, recurrent (episodic) and systemic mast cell activation (MCA), 2) increase in tryptase level to plus 20 % + 2 ng/ml within a 1-4 hours after onset of the acute crisis, 3) response of MCA symptoms to antimediator therapy. Classification of MCAS requires applying highly sensitive and specific methodological approaches for assessing clonal bone marrow mast cells (BM MCs) at low frequencies. The Spanish Network on Mastocytosis (REMA) score is successfully used as predictive model for selecting MCAS candidates for BM studies based on a high probability of having an underlying clonal mast cell disorder (c-MCD). In this article, we propose a diagnostic algorithm and focus in the practical evaluation and management of patients with suspected MCAS.