Nontuberculous Mycobacterial Infection Mimicking Inflammatory Tenosynovitis: A Real Head Scratcher

Area of Science:

• Infectious Diseases
• Rheumatology
• Orthopedic Surgery

Background:

• Nontuberculous mycobacterial (NTM) tenosynovitis is a rare condition frequently misdiagnosed as bacterial or inflammatory tenosynovitis.
• Early presentation often involves wrist pain and swelling, mimicking more common conditions.

Observation:

• A 64-year-old man presented with chronic wrist pain and swelling.
• Initial MRI showed tenosynovitis; surgical debridement revealed reactive histopathology with negative infectious work-up.
• Despite treatment with steroids and disease-modifying antirheumatic drugs, symptoms persisted and progressed.

Findings:

• Repeat biopsy eventually identified acid-fast bacilli (AFB) on staining and culture, confirming NTM tenosynovitis.
• The patient responded well to a multi-drug regimen including clarithromycin, ethambutol, and rifampin.

Implications:

• This case highlights the importance of considering NTM tenosynovitis in persistent, unexplained tenosynovitis, especially with negative initial work-ups.
• Open tissue biopsy is critical for diagnosis when clinical response to standard treatments is lacking.
• Timely diagnosis and appropriate antimicrobial therapy are essential to prevent disease progression and improve outcomes.