Skin Disease in Mastocytosis

Abstract

The hallmark of mastocytosis is the pathological accumulation of mast cells in various tissues. The skin is the most frequently affected organ, followed by bone marrow. Cutaneous mast cell infiltration is usually associated with typical skin lesions. According to the morphology of the lesions, three subforms are distinguished, namely maculopapular cutaneous mastocytosis, diffuse cutaneous mastocytosis and cutaneous mastocytoma. Maculopapular cutaneous mastocytosis is further subdivided into a monomorphic and a polymorphic variant. An important diagnostic feature of all subforms is a positive Darier’s sign. There are significant clinical differences in skin lesions based on the age of disease onset. Paediatric patients often show cutaneous mastocytoma or the polymorphic variant of maculopapular cutaneous mastocytosis, normally without systemic involvement, and a transient disease course with spontaneous remission after several years. By contrast, adults typically present with the monomorphic variant of maculopapular cutaneous mastocytosis, usually associated with systemic mastocytosis and a chronic or progressive course. Patients with skin lesions, regardless of whether bone marrow and other organs are involved, can experience mast cell mediator symptoms such as pruritus, anaphylaxis, flushing and diarrhoea. The current treatment mainly aims at reducing mediator symptoms using antihistamines and, if indicated, also adrenaline, corticosteroids, sodium cromoglycate, specific immunotherapy and omalizumab. Preliminary study results indicate that specific tyrosine kinase inhibitors will soon also become relevant in the treatment of skin involvement in mastocytosis.