Paediatric mastocytosis: long-term follow-up of 53 patients with whole sequencing of KIT. A prospective study

Abstract : Background Mastocytosis is a heterogeneous group of clinical disorders characterized by the abnormal accumulation of mast cells. The adult and paediatric forms differ in their clinical and genetic features and outcomes. ObjectivesMethodsTo describe the clinical evolution of a well-characterized cohort of paediatric mastocytosis (PM), and to analyse the relationship between KIT mutation and the clinical course. This was a prospective cohort study performed at the National Clinical Reference Center for Mastocytosis. Diagnosis was confirmed by identification of KIT mutation on lesional skin biopsy. Mastocytosis subtype, mast cell mediator-related symptoms (MC MRS) and clinical course were recorded. Fifty-three patients with PM and >4years of disease course were enrolled. The meanSD age at the final evaluation was 13248years. The main outcome was the type of KIT mutation as a predictor of evolution and clinical characteristics. ResultsConclusionsPatients presented with maculopapular cutaneous mastocytosis (n=44), diffuse cutaneous mastocytosis (n=6) or mastocytoma (n=3). The mean duration of disease was 121years. Substantial or partial cutaneous regression (18 of 53 and 16 of 53), stabilization or aggravation (16 of 53) and complete cutaneous regression (three of 53) were noted. MC MRS mainly regressed (21 of 53). For 22 patients, evolution of MC MRS and evolution of cutaneous lesions were different. No significant association between evolution and KIT mutation or between evolution and type of cutaneous mastocytosis was found. A late onset of the disease (after 2years) is associated with worse evolution. PM is not systematically self-regressive. MC MRS manifestations and cutaneous lesions can persist or increase overtime. KIT mutation is not a predictor of evolution.