A Case of Mycobacterium Marinum Infection in the Middle Finger of the Left Hand.

Abstract

Background: In April 2024, our hospital confirmed a case of Mycobacterium marinum infection in the middle finger of the left hand. The patient sought medical attention at our hospital due to swelling of the left middle finger with tendon contracture for one and a half years and subcutaneous induration of the left palm for one month. In September 2022, the patient's left middle finger was pricked by raw fish bones, resulting in punctate erythema and pain. Self-application of erythromycin ointment did not improve. In November 2022, the left middle finger showed redness and swelling. The local hospital diagnosed it with tenosynovitis, but the effect of anti-inflammatory treatment was not significant. Later, the left middle finger gradually developed tendon contracture and mobility disorders. In May 2023, the patient underwent multiple "short needle knife" treatments in an external hospital for "tenosynovitis". The swelling and redness of the fingers slightly subsided, and the treatment effect was not ideal. In March 2024, the patient developed subcutaneous induration in the left palm. For additional diagnosis and treatment, the patient went to our hospital for treatment. Clinically admitted with "1. Hand skin infection (Mycobacterium), 2. Tendon contracture (with infection)".

Methods: Clinically, ultrasound-guided puncture and aspiration of subcutaneous abscess in the middle finger of the left hand were performed. The extracted pus was subjected to bacterial culture and identification, acid fast staining, Gram staining, NGS (Next-Generation Sequencing) detection of pus and additional related auxiliary examinations such as blood routine, urine routine, liver function, kidney function, and electrocardiogram.

Results: Hand magnetic resonance imaging: 1. Abnormal signals around the third proximal phalanx of the left hand and around the flexor tendon of the third metacarpal finger, suspected of abscess. 2. Increased signal in the left wrist canal, suspected of inflammatory disease. Blood routine + CRP (venous blood): The percentage of neutrophils is 28.9%, the total number of neutrophils is 1.30 x 109/L, and the percentage of lymphocytes is 60.2%. Liver function: Total protein 58.0 g/L, albumin 33.6 g/L, no significant abnormalities observed in the rest. Acid fast staining of pus: positive, culture and identification of pus bacteria (MALDI-TOF MS, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry): Mycobacterium marinum. NGS detection of pus: Mycobacterium marinum. Clinical treatment plan: Rifampicin 0.6 g po qd, clarithromycin 0.5 g po bid for anti-infection treatment, local hot compress. After 5 days of treatment, the patient's flexor digitorum tendon extended towards the proximal end, with a soft texture and mild tenderness. The flexion activity was slightly restricted, and no additional special discomfort was reported. The patient improved and was discharged.

Conclusions: This article reports a case of Mycobacterium marinum infection in the middle finger of the left hand. Mycobacterium infection was quickly and accurately identified by MALDI-TOF MS and NGS, reasonable treatment measures were adopted clinically. The patient improved and was discharged. I hope that in the future, this study can provide assistance for the clinical diagnosis and treatment of Mycobacterium infection.