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A 10 month old boy was referred with recurrent urticaria. There had been five episodes over two months, one associated with facial swelling and respiratory distress. Each episode responded quickly to antihistamines. On examination there was a 3×1.5 cm flat brown birthmark on his lower back. Gentle palpation triggered this dramatic urticarial reaction over his trunk and limbs that resolved with antihistamine (see fig 1).
Dermatological review confirmed the clinical diagnosis of mastocytoma, and he commenced regular antihistamine treatment.
Cutaneous mastocytosis is a rare condition, usually presenting in the first two years of life.1 It is characterised by mast cell hyperplasia, either as a solitary mastocytoma or as multiple ovoid red-brown macules known as urticaria pigmentosa. Diffuse cutaneous mastocytosis is less common. Physical stimulation of the lesion, such as by rubbing, triggers mast cell degranulation causing local erythema, oedema, and pruritus. This localised urtication is known as Darier’s sign. Temperature change may also precipitate symptoms.2 Vesiculation or frank blistering of lesions occurs commonly in infancy and may be confused with bullous impetigo, epidermolysis bullosa, or cigarette burns.3 Acute systemic symptoms such as flushing, hypotension, and wheeze are more frequent in patients with extensive cutaneous disease, so our patient was unusual in experiencing wheeze and facial swelling.
Treatment is symptomatic with antihistamines and/or mast cell stabilisers. Biopsy and excision should be avoided due to the risk of profound histamine release during surgery. Prognosis is good, with lesions and symptoms frequently resolving by adulthood.1–3
Competing interests: none
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