Mycobacterium marinum Infection Misdiagnosed as Skin Lesions of Sjögren's Syndrome: A Case Report of Fishbone Injury and Literature Review.

Cutaneous infections caused by Mycobacterium marinum are rare. We report a case initially misdiagnosed as skin lesions associated with Sjögren's syndrome but clinically highly suspected of Mycobacterium marinum infection, and we review the relevant literature. The patient was a 39-year-old male with a prior history of Sjögren's syndrome. Following an accidental fishbone injury at work, he developed skin redness, swelling, and ulceration on the right middle and little fingers, which was subsequently followed by multiple nodules on the dorsum of the right hand and upper limb. After debridement, suturing, and pathological biopsy, the wound showed delayed healing for four months, with persistent redness, swelling, suppuration, and exudation. Three weeks after initiating empirical treatment with oral clarithromycin combined with rifampicin, the wound redness and swelling subsided, and the lesion healed with crust formation. Based on the patient's history of fishbone injury, characteristic skin lesions, histopathological findings, and response to empirical treatment, although the causative pathogen has not been definitively identified, a clinical suspicion of Mycobacterium marinum infection was made.