CPC03 Unusual cases of scalp ulceration: two distinct diagnoses

Abstract Scalp ulceration can present as a challenging diagnostic entity, especially when involving rare or atypical conditions. Here, we report two distinct cases manifesting as scalp ulcerations but caused by entirely different underlying diseases: limited granulomatosis with polyangiitis (GP) and scalp actinomycosis. Case 1: limited granulomatosis with polyangiitis. A 21-year-old woman presented with multiple nonhealing ulcers, preceded by pustules over the scalp, right forearm and breast for 6 months and subcutaneous swelling over the frontal region for 1 month. Examination revealed deep ulcers involving all layers of the scalp to the pericranium, exposing cranial bones, and similar ulcerative lesions on the forearm and breast. Histopathology revealed granulomas with vasculitis, supported by imaging findings of pansinusitis and mastoiditis. Based on the American College of Rheumatology classification criteria, she was diagnosed with limited GP. She was treated with injectable steroids and cyclophosphamide, leading to peripheral healing of the lesions and significant improvement. A 9-month follow-up showed no recurrence. This case underscores the importance of recognizing GP as a potential cause of scalp ulceration, especially in the presence of systemic granulomatous inflammation and vasculitis. Case 2: scalp actinomycosis. A 10-year-old girl presented with multiple scalp swellings persisting for 5 years, following trauma to the forehead at the age of 3 years. Examination revealed erythematous to red, polypoidal nodules with crusting and purulent discharge. Imaging demonstrated hyperdense lesions with dural thickening and irregularities of the skull bone, while biopsy revealed neutrophilic infiltrates and bacterial filaments displaying the Splendore–Hoeppli phenomenon, confirming actinomycosis. The patient was treated initially with injectable ceftriaxone for 3 weeks, followed by oral penicillin G due to the unavailability of penicillin injections. Complete resolution of lesions was observed within 1 month. Actinomycosis, a rare soft-tissue infection, is often misdiagnosed due to its mimicry of malignancy or other infections. This case highlights its unusual presentation and the efficacy of ceftriaxone as an alternative treatment. Both cases represent rare and unusual manifestations of scalp ulceration caused by distinct aetiologies – autoimmune and infectious. While GP involves necrotizing granulomatous inflammation and vasculitis, actinomycosis results from bacterial infection, often requiring a breach in the epithelial barrier. The clinical presentations of both diseases overlap in terms of chronicity and ulcerative lesions, underscoring the importance of diagnostic evaluation, including imaging, histopathology and microbiological studies. Treatment modalities differ significantly, with GP requiring immunosuppressive therapy, and actinomycosis responding to prolonged antibiotic treatment. These cases highlight the diverse differential diagnoses of scalp ulceration and the need for a multidisciplinary approach to accurately identify and manage these rare conditions.