A Case of Skin and Soft Tissue Infection Complicated by Infectious Tenosynovitis Caused by Mycobacterium fortuitum in an Immunocompetent Child

Abstract

Introduction: Nontuberculous mycobacteria (NTM) are an uncommon cause of skin and soft tissue infections (SSTIs) in immunocompetent children and often pose diagnostic challenges. Among rapidly growing mycobacteria, Mycobacterium fortuitum can cause progressive SSTIs; however, optimal antimicrobial strategies in pediatric patients remain insufficiently defined. Case Presentation: We report a case of SSTI of the right upper extremity caused by M. fortuitum in a previously healthy child. Initial β-lactam and macrolide therapies were ineffective. Combination therapy with linezolid (LZD) and trimethoprim–sulfamethoxazole (TMP–SMX) resulted in transient clinical improvement. However, LZD was discontinued because of bone marrow suppression, and the infection subsequently progressed during TMP–SMX monotherapy. Magnetic resonance imaging revealed infectious tenosynovitis of the extensor tendons extending from the dorsum of the right hand to the forearm, necessitating surgical debridement. Postoperatively, the patient received negative pressure wound therapy and approximately four weeks of inpatient multidrug therapy with amikacin, imipenem/cilastatin, and TMP–SMX. At discharge, treatment was switched to oral levofloxacin (LVFX) plus TMP–SMX and continued for five months, for a total of six months of antimicrobial therapy following surgical debridement. No recurrence was observed during follow-up. Conclusions: This case highlights the importance of sustained combination antimicrobial therapy and timely surgical intervention and suggests that long-term oral LVFX plus TMP–SMX may be a feasible maintenance therapy option for a pediatric M. fortuitum SSTI with tenosynovitis.