PA17 Paediatric-onset mastocytosis: a retrospective review

Abstract

Abstract Mastocytosis is characterized by an abnormal accumulation of mast cells in different organs. The skin is the most frequently affected site. Most cases of paediatric-onset mastocytosis are benign, localized to the skin and regress spontaneously. We retrospectively reviewed the case notes of paediatric patients with a diagnosis of mastocytosis in dermatology departments within our region between 2021 and 2022. Seventeen patients were identified. The disease was more prevalent in males (male-to-female ratio 1.8s : 1). The median age at onset was < 1 year (range birth–4 years). The lesions were described as solitary (n = 9), macular (n = 6) and maculopapular (n = 2). The torso was involved in 16 patients. Other body sites affected were the face (n = 2), scalp (n = 1), limbs (n = 5) and buttock (n = 2). Most patients were asymptomatic (n = 12). Symptoms, including abdominal pain (n = 3), pruritus (n = 2), musculoskeletal pain (n = 1), diarrhoea (n = 1), flushing (n = 1), headache (n = 1) and dizziness (n = 1), were reported. Darier sign was positive in 11 patients and negative in three (not documented in three). None of the patients had bone marrow examination. One patient underwent a skin biopsy, which confirmed mastocytosis in the skin; the remaining 16 patients were diagnosed with cutaneous mastocytosis based on the characteristic clinical features. The disease was classified into mastocytoma (n = 8) and urticaria pigmentosa (n = 9). Five patients with urticaria pigmentosa were assessed for lymphadenopathy and organomegaly: four had blood investigations, including serum tryptase (n = 4), full blood count (n = 2) and liver function tests (n = 2); one had an abdominal ultrasound. No abnormality was found. Patients with mastocytoma were not examined for lymphadenopathy or organomegaly, or had further investigations for systemic involvement. Eight patients were managed by watchful monitoring. Nine patients received active treatments, including topical steroids (n = 6), antihistamines (n = 6), oral sodium cromoglicate (n = 1), phototherapy (n = 1), epinephrine autoinjector (n = 1) and cosmetic camouflage (n = 1). Partial regression was observed in seven cases at a median follow-up of 3 years (range 1–14), and seven had persistent disease. Six patients remain under long-term follow-up, and eight were discharged with a median follow-up period of 1.5 years (range 1–14). Five patients were followed to adolescence (disease was persistent in three cases and there was partial regression in two cases; none had complete resolution). While serum tryptase levels do not appear to have a prognostic value in the paediatric population, we would recommend checking these in patients whose disease persists beyond adolescence as this may indicate progression to systemic mastocytosis.