Mycobacterium marinum Infection: A Clinical Case Report and 5-Year Systematic Literature Review (2021-2025).

We report a case of cutaneous Mycobacterium marinum infection in a 66-year-old male patient with traumatic aquatic exposure, manifesting as multiple red nodules and plaques (1-2 cm in diameter) showing typical sporotrichoid (lymphocutaneous) distribution extending from the extensor knuckle of the right index finger to the right forearm, accompanied by partial rupture and purulent exudation. Histopathological examination of skin biopsy specimens demonstrated infectious granuloma formation, and combined bacterial culture, hsp65 PCR and next-generation sequencing (NGS) confirmed M. marinum as the causative pathogen. M. marinum is an opportunistic nontuberculous mycobacterium (NTM) colonizing aquatic environments, which invades human skin via traumatic wounds. Its non-specific cutaneous manifestations frequently lead to diagnostic delay and misdiagnosis. We further conducted a systematic literature review covering all published M. marinum cutaneous infection cases from 2021 to 2025 to summarize clinical characteristics, diagnostic strategies and standardized treatment regimens. This case report highlights critical diagnostic pitfalls of M. marinum infection, stresses that clinicians should maintain a high clinical suspicion for NTM infection in patients with aquatic trauma history, and compares multi-modal diagnostic tools (histopathology, culture, PCR and NGS). We also summarize adjustments to immunosuppressive agents for immunocompromised patients with M. marinum infection, providing practical clinical references to shorten diagnostic time and improve therapeutic prognosis.