A Rare Case of Actinomycosis in a Patient With Systemic Lupus Erythematosus

Actinomycosis is a rare, chronic infection caused by Actinomyces species, which are normal commensals of human mucosa. It commonly involves the orocervicofacial, thoracic, abdominal, and pelvic regions. It can also affect other sites, such as cutaneous tissue, as seen in our case. We report a case of a 35-year-old woman with systemic lupus erythematosus (SLE) and lupus nephritis on immunosuppressive therapy who developed a large, nodular cutaneous actinomycosis lesion over the right calf. A biopsy confirmed Actinomyces, and she responded to a six-month course of amoxicillin-clavulanate. However, the lesion recurred a year later, requiring surgical excision due to persistent disease despite prolonged antibiotic therapy. Over a two-year follow-up, no further recurrence was noted. This case highlights the diagnostic challenges of cutaneous actinomycosis, particularly in SLE patients, and emphasizes the role of histopathological confirmation, prolonged antibiotic therapy, and surgical intervention when necessary.