Clinical Approach to MCAS Diagnosis and Cutaneous Mastocytosis

Table 1. Variants of MCAS

Clonal (primary) MCAS	- Mastocytosis (cutaneous, systemic) - Clonal MCAS - KIT D816V mutation, with or without CD2 and/or CD25 positivity
Secondary MCAS	- IgE-mediated allergy or other hypersensitivity - Physical urticarias - Inflammation: neoplasm, autoimmune, infection [4]
Combined/Mixed MCAS	Two or more of the following present:- Cutaneous or systemic mastocytosis - Allergy or atopic disease - Genetic predisposition (ex. HαT – whether this disorder involves inherent MC activation (MCA) is still being studied; it has not yet been proven that HαT directly involves heightened MCA versus being a modifier and/or facilitator of other MCAS [5-7]
Idiopathic MCAS	None of the following: - Neoplastic/clonal MCs - IgE-dependent allergy