Given the renewed focus on mastocytosis (recognized in Italy as a rare disease since 2018) and emerging clinical and immunogenetic knowledge, and considering the rarity of the disease and limited understanding of its progression, this observational study aims to analyze epidemiological, clinical, genetic, immunohistochemical, and laboratory characteristics of patients with mastocytosis. This will help expand knowledge about the disease and identify prognostic variables useful in developing a personalized therapeutic approach. This registry aims to collect retrospective and prospective data on patients with cutaneous and systemic mastocytosis attending the Dermatology Unit at the IRCCS Fondazione Policlinico San Matteo. This is a single-center longitudinal hospital registry including patients with cutaneous and systemic mastocytosis, collected retrospectively and prospectively to assess the clinical, serological, hematological, and molecular characteristics of patients with cutaneous and systemic mastocytosis and their correlation with specific outcomes such as disease variant (cutaneous or systemic), extent of skin involvement, and survival rate.