Phenotypic and Genotypic Characteristics of Mastocytosis Differ According to the Age of Disease’s Onset.

Mastocytosis is a heterogeneous group of disease with respect to clinical, biological and genotypic features, which may either occur during childhood or at the adult’s age. Adult’s mastocytosis is usually associated with persistent systemic involvement and c-kit 816 mutations, while pediatric’s disease is mostly limited to the skin and often resolves spontaneously during adolescence. No study has attended to compare characteristics of adult’s mastocytosis according to the age of disease’s onset. Among 155 adult patients with histologically proven cutaneous mastocytosis and complete phenotypic and genotypic data available recruited through the French mastocytosis network (AFIRMM), disease started before 15 years in 23 patients (15%) and later than 18 years in 132 patients (85%). We compared phenotypic and genotypic features of patients whose disease started during childhood (Group 1, n = 23) with those of 31 randomly allocated patients whose disease started at adult’s age (Group 2). Genotypic analysis was performed on skin biopsy by direct sequencing of c-kit exons 17 and 8 to 13 in which most of activating mutations are found. According to the WHO classification, the percentage of systemic disease was similar in both groups (61 vs. 79%) in groups 1 and 2, respectively. Bone pain (57% vs. 23%) and flush (83% vs. 39%) differ between groups (p