Mycobacterium marinum Infection in a Patient on Certolizumab Treated with Combined Antibiotics and Photodynamic Therapy: A Case Report

Introduction

Mycobacterium marinum (M. marinum) is a non-tuberculous mycobacterium associated with aquatic environments, causing infections ranging from cutaneous disease to disseminated forms. Management is variable and may be complicated by immunosuppression. Case Presentation: We report a case of M. marinum infection in a 71-year-old man with psoriatic arthritis receiving certolizumab pegol, a TNF-alpha inhibitor (TNFi). He developed a forearm rash after brackish water exposure, initially suspected to be sporotrichosis but later confirmed as M. marinum. Rifampin and ethambutol were initiated, and certolizumab was held; however, treatment was complicated by antimicrobial side effects and a psoriatic arthritis flare requiring TNFi reinitiation. After a prolonged clinical plateau, the patient ultimately improved with the addition of adjunctive photodynamic therapy (PDT) and local heat application alongside a better-tolerated combination antimicrobial regimen.