Figure 2. Mast cell–related disorders.

Diseases associated with mast cells can broadly include disorders associated with extrinsic factors, such as the ones mediated by IgE antibodies that, acting through the high-affinity IgE receptor (FcεRI) expressed on the mast cell surface, can translate into the development of allergic reactions. Allergies are detrimental immune responses against otherwise innocuous environmental antigens, which induce the production of IgE antibodies that can activate mast cells, eventually leading to, for example, allergic rhinitis, asthma, and atopic dermatitis ²⁶. Excessive allergic reactions can translate into anaphylaxis. Other disorders can instead be cell-intrinsic, due to altered biological features of mast cells that lead to uncontrolled responses (mast cell activation syndrome, or MCAS) ³¹ or excessive proliferation (systemic and cutaneous mastocytosis, or SM and CM). Potentially, all mast cell disorders can display altered activation and are broadly defined as mast cell activation disorders (MCADs), although MCAS represents a subgroup displaying mast cell activation without clonal expansion ^{32, 33}.