Primary Cutaneous Nocardiosis in an Immunocompetent Patient

A healthy 42-year-old Japanese woman presented with a 7-day history of a painful palpable mass under her chin (Picture A). A computed tomography scan demonstrated a subcutaneous abscess (Picture B and C), which was aspirated by an otolaryngologist. Kinyoun staining of the specimen showed positive results (Picture D), and the organism was identified as Nocardia brasiliensis by culture and 16s rRNA gene sequencing. The blood culture results were negative. Antibiotic treatment with oral trimethoprimsulfamethoxazole was initiated, which was switched to amoxicillin/clavulanic acid due to a drug allergy. The abscess resolved with 12 weeks of treatment. Primary cutaneous nocardiosis is rare and is most commonly caused by Nocardia brasiliensis (1). The manifestations include ulceration, pyoderma, cellulitis, nodules, and subcutaneous abscesses (2). It usually occurs in immunocompetent individuals (1) and should thus be considered in the differential diagnosis of subcutaneous abscess in such patients. Aspiration and a microbiological investigation are therefore necessary to confirm the diagnosis.