Mastocytosis

Abstract Mastocytosis is caused by a clonal expansion of neoplastic mast cells. It usually presents in the skin, bone marrow or both but may affect other tissues. Children with cutaneous mastocytosis present with urticaria pigmentosa, mastocytomas or diffuse cutaneous mastocytosis. Around 50% will remit spontaneously before adulthood. Most adults have indolent systemic mastocytosis and carry the D816V KIT mutation. A few will progress to advanced disease. Risks include anaphylaxis, reduction in bone density and the development of associated haematological disorders. Cutaneous symptoms include itching, hiving and flushing. Bowel symptoms include dyspepsia, pain and diarrhoea. Neuropsychiatric symptoms of fatigue, depression and ‘brain fog’ may occur. Diagnosis is confirmed on biopsy of skin, bone marrow or other tissues. Baseline blood tryptase is a useful marker of mast cell load. Management is primarily symptomatic and supportive although cytoreductive treatments may be necessary for advanced presentations causing organ damage. Targeted novel tyrosinase kinase inhibitors are under development.