Whilst the introduction of new systemic treatment options for the management of patients affected by CM, such as immunotherapies (anti-CTLA-4 and anti-PD-1 antibodies [76]) or targeted therapies (BRAF, MEK inhibitors [77]) either alone or in combination, represented a significant breakthrough in clinical practice, the development of systemic therapies for MMs has been much slower [7]. The gene discussed is CTLA4; the disease is cutaneous mastocytosis.