Refractory minimal change disease associated with Mycobacterium marinum infection.

This case report describes a rare instance of minimal change disease (MCD) associated with Mycobacterium marinum infection. MCD is typically idiopathic but can occasionally occur secondary to infections. The patient was a 61-year-old fisherman with a history of relapsing MCD who developed a subcutaneous abscess in the lower leg while undergoing rituximab and glucocorticoid therapy. Ziehl-Neelsen staining revealed acid-fast bacilli, and culture at 30 °C isolated M. marinum, a slow-growing nontuberculous mycobacterium (NTM) commonly found in aquatic environments. The infection was attributed to the combination of occupational exposure and immunosuppression. Targeted antimicrobial therapy with clarithromycin, minocycline, and rifampicin led to resolution of the abscess and complete remission of MCD, suggesting a causal link between the infection and disease relapse. This case highlights several key clinical considerations. First, secondary infectious causes should be evaluated in patients with treatment-resistant nephrotic syndrome. Second, appropriate laboratory techniques, including optimized culture conditions, are critical for identifying rare NTM. Third, a detailed assessment of lifestyle and occupational exposures can provide essential diagnostic clues. The report underscores the importance of vigilance in atypical or refractory MCD cases and supports the role of targeted antimicrobial therapy in resolving both infection and associated nephrotic syndrome.