Adjunctive use of photodynamic therapy in refractory cutaneous granuloma caused by Mycobacterium marinum infection: A case report

Mycobacterium marinum is a major species of nontuberculous mycobacteria (NTM) responsible for skin infections, commonly affecting aquatic animals and humans. The typical histopathological pattern of cutaneous M. marinum infection is suppurative granuloma. Antibiotics are the first-line treatment; however, they often require prolonged courses, are associated with significant side effects, and carry a risk of drug resistance. Aminolevulinic acid photodynamic therapy (ALA-PDT) represents a safe and effective therapeutic option for cutaneous M. marinum infections, particularly in drug-resistant cases. This report describes a patient with cutaneous granuloma caused by M. marinum infection who showed no significant improvement after two months of oral triple-antibiotic therapy. Subsequently, while continuing oral antibiotics, the patient underwent ALA-PDT once weekly for 4 consecutive weeks. Following four treatment sessions, the nodules, plaques, and ulcers on both the wrist and forearm were completely eradicated, with no recurrence observed during the 6-month follow-up period. This case suggests that adjunctive ALA-PDT, acting locally, can potentially reduce treatment duration and minimize systemic antibiotic-related side effects and adverse reactions, offering a valuable alternative for patients with suboptimal responses to antibiotic therapy alone.