Systemic mastocytosis and recurrent anaphylactic shock

RAST IgE, and serotonin metabolite levels, were normal except for elevated histamine (2.19 ng/mL, NR: 0.11-0.50 ng/mL) The histamine level returned to normal one month later. The histamine release test was negative. Skin and bone marrow biopsies showed an increase in the number of mast cells (figure). We diagnosed systemic mastocytosis and treated the patient with antihistamines; epinastine hydrochloride (an H1 antagonist commonly used in Japan) and famotidine (an H2 antagonist). When last seen, in May, 2002, she was in good health and had suffered no further episodes of syncope. Mastocytosis is an abnormal increase in the number of mast cells.1 The skin is involved in up to 90% of patients, manifesting as pruritus, urticaria, and dermatographism. Systemic mastocytosis is characterised by diffuse mast-cell infiltration of multiple organs and may affect approximately 10% of all patients with mastocytosis. Estimates of the proportion of cases of systemic mastocytosis in which there is no cutaneous involvement vary from 10-50%.2 A mast-cellderived mediator causes prolonged episodes of flushing lasting 15-30 min and associated with headache, dyspnoea, chest pain, nausea, diarrhoea, paraesthesias, warmth, palpitations or lightheadedness. Less common features include anaphylaxis and syncope.' Diagnosis based on elevated levels of mast-cell-derived mediators, such as plasma histamine levels, can be difficult.