P105 Adult-onset mastocytosis: a retrospective review

Abstract

Abstract Mastocytosis is characterized by an abnormal proliferation of mast cells in different organs, with the skin being the most frequently affected site. Adult-onset mastocytosis often follows a chronic course and is more likely to have extracutaneous involvement. We undertook a retrospective case note review of adult patients with a diagnosis of mastocytosis in our dermatology department between 2021 and 2022. Fourteen patients were identified with a female-to-male ratio of 1.8 : 1. Median age at disease onset was 46 years (range 25–75). Lesions were described as maculopapular (n = 8), macular (n = 3), telangiectatic (n = 2) and urticated (n = 1). The torso was affected in 12 patients (86%). The most commonly reported symptom was pruritus (n = 9). Other complaints included flushing (n = 3), abdominal pain (n = 2), dizziness (n = 2), weight loss (n = 2), night sweats (n = 2), syncope (n = 1), musculoskeletal pain (n = 1) and symptoms of recurrent anaphylaxis (n = 1). Two patients were asymptomatic. Darier sign was elicited in five patients and negative in two (not documented in seven). Eight patients were assessed for lymphadenopathy and organomegaly, with no detected abnormality. Eleven patients had skin biopsies; 10 (91%) had mastocytosis in the skin confirmed on histology; one patient had a nondiagnostic histological finding, but mastocytosis was diagnosed on the basis of clinical presentation. Seven patients had elevated serum tryptase levels (> 20 ng mL−1) on at least one occasion. Bone densitometry was done in five patients with elevated serum tryptase: two had osteopenia and one had osteoporosis. Eleven patients underwent bone marrow examination. Mast cell infiltration of the bone marrow was detected in four patients; KIT mutations in bone marrow were subsequently identified in three patients. Twelve patients remain under long-term follow-up. Treatments prescribed included antihistamine (n = 10), epinephrine autoinjector (n = 6), topical steroids (n = 5), vitamin D (n = 5), calcium (n = 4), H2 blocker (n = 2), bisphosphonates (n = 2), phototherapy (n = 2), leukotriene antagonists (n = 2), cosmetic camouflage (n = 1), oral sodium cromoglicate (n = 1) and KIT–tyrosine kinase inhibitor (n = 1). Despite treatments, none of the patients had regression (partial or complete) of cutaneous disease, although no fatal outcome was observed. Four (29%) cases had a final diagnosis of indolent systemic mastocytosis (all had elevated serum tryptase levels, two had anaemia). Our findings were consistent with the literature, where serum tryptase levels rather than systemic symptoms were a reliable predictor of systemic mastocytosis. Interestingly, 10 (71%) patients had mastocytosis limited to the skin, which is in contrast to the published literature, where the majority of people with adult-onset mastocytosis have systemic forms of the disease.