O03 Langerhans cell histiocytosis: case series of presentations to dermatology in the BRAF era

Abstract Langerhans cell histiocytosis (LCH) is a rare disease driven by MAPK pathway mutations. This condition is on a spectrum, from single-system to life-threatening multisystem disease. Identification of the BRAF mutation is leading to improved understanding and targeted therapies. However, there is limited information on genetic status, phenotype and dermatological features. Fourteen patients were seen in the Paediatric Dermatology department in period 2015–2022: 11 males and 3 females; 9 patients had multisystem LCH; 8 patients had cutaneous manifestations of LCH; and 4 had limited cutaneous LCH. Six patients were diagnosed in the department and typically had multiple incorrect diagnoses and treatments prior to review. Clinical features varied from widespread skin involvement, scalp/groin intertrigo, flexural ulcerations and telangiectatic papules. Eight had LCH diagnosed in other tissues by oncology and referral advice on cutaneous symptoms were sought. Most patients have required input from dermatology throughout treatment. Biopsies were taken when unclear diagnosis and/or pathology would influence treatment. Several consultations revealed benign pathologies including keratosis pilaris and dermatitis requiring topical treatment advice only. All five patients with BRAF v600 mutation had multisystem disease including diabetes insipidus, adrenal insufficiency, gut and bone lesions. Two patients with severe LCH and BRAF mutations are being treated successfully with dabrafenib. Our series demonstrates the important role of dermatology in the diagnosis and management of LCH. This series confirms clinical heterogeneity and an association of BRAF V600E mutation with multiorgan disease. Ongoing work should expand our knowledge of the relationship of genetic alterations with clinical phenotypes and comorbidities.