Analysis of Clinical Features of Patients with Cutaneous Mycobacterium marinum Infections: A Cohort Study

Objective: Mycobacterium marinum infections represent increasingly common diagnostic and therapeutic challenges. This descriptive study integrated institutional and literature cases to analyze clinical features and inform management strategies. Methods: We reviewed 20 cases of M. marinum infection from the Hospital for Skin Diseases, Institute of Dermatology, Chinese Academy of Medical Sciences & Peking Union Medical College (January 2022–December 2024) and 52 literature cases from the same period. Descriptive statistics were conducted to analyze demographics, exposure history, clinical manifestations, diagnostic methods, and treatment responses. The chi-square test or Fisher’s exact test was utilized for categorical variables; t-tests were used for continuous variables. Results: Data from 72 cases were included. The mean age was 51.56 ± 14.80 years (range: 3.00–78.00; median: 53.50), and the male-to-female ratio was 1:1.32. Fifteen patients (20.8%) were non-Chinese. Sixty-one (84.7%) reported a precipitating factor, and 18 (25.0%) had systemic diseases. Unilateral upper extremity involvement occurred in 68 cases (94.4%), with local nodules as the predominant manifestation (Type II, 55 cases, 76.4%). Diagnoses relied on clinical findings, pathology (55/63 with typical granulomas), mycobacterial culture (54/67 positive), and mRNA amplification assays (57/63 positive). Treatment primarily involved dual (39 cases, 54.2%) or triple antibiotic regimens (23 cases, 31.9%) over 5.65 ± 3.02 months (range: 0.50–14.00; median: 5.50). Sixty patients (83.3%) achieved cure; the follow-up rate was low (32 cases, 44.4%). Among Chinese patients, most were female with predominantly Type II lesions; non-Chinese patients were mostly male, with nearly equal proportions of Type II and Type III disease (all P <0.05). Conclusion: M. marinum infections primarily affect middle-aged and older individuals, regardless of immunocompetence, often with identifiable triggers. Long-term combination antibiotic therapy remains the main treatment. Despite limitations including single-center data, literature-derived case biases, small sample size, and low follow-up rates, our findings may support earlier diagnosis and more effective treatment of M. marinum infections.