Successful treatment of atypical mycobacteriosis of the scalp with photodynamic therapy

Dear Editor, A 74-year-old Caucasian man was referred to our unit for evaluation of a persistent erythematous plaque affecting the occipital region of the scalp. The patient referred that the lesion had been present for more than a year and was asymptomatic. The borders of the lesion were poorly demarcated, whereas its surface was scaly and did not present any ulcerations (Figure 1). A skin biopsy and a culture test had previously been performed at another hospital, revealing an atypical mycobacteriosis (AM) due to Mycobacterium marinum. The patient had already been treated with systemic anti-infective therapy (oral rifampicin plus clarithromycin for 6 months), which had achieved only a slight improvement. He could not remember any previous local traumas or injuries in the occipital region; he was otherwise healthy and blood tests were within the normal ranges. Dermoscopy revealed an orangish, homogeneous background with fine surface scales and linear irregular vessels with variable diameters (Figure 2A,B). A cycle of five sessions of conventional photodynamic therapy (PDT) was therefore undertaken, using the photosensitizing agent methyl aminolevulinate (MAL) (METVIX Cream, Galderma Medical Solutions) left under occlusion for 3 hours, then illuminated with a red light-emitting diode lamp (Aktilite CL128, Galderma, wavelength 630 nm). MAL-PDT was performed once a month, at increasing dosages from 37 to 60 J/cm (irradiation time ranging from 8:30 to 14:30 minutes). The treatment was well tolerated by the patient. A progressive improvement, both clinically and dermoscopically, was observed from one session to another (Figure 3A-F). A complete healing and resolution of the clinical picture was achieved after the F IGURE 1 Atypical mycobacteriosis of the scalp presenting as a persistent erythematous plaque affecting the occipital region, with poorly demarcated borders, surface scales, and absence of ulceration