Cutaneous Rhodococcus equi Infection in an Immunocompetent Host: A Case Report.

Rhodococcus equi is a zoonotic Gram-positive bacterium that can affect immunocompetent hosts and only rarely presents with cutaneous lesions resembling other granulomatous dermatoses, such as cutaneous mycobacterial infections, deep fungal infections, sarcoidosis, and foreign body granulomas. This report describes a 53-year-old immunocompetent woman who developed recurrent ulcerated nodules on the left lower extremity following recreational travel to southern Mexico. Initial diagnostic studies were nondiagnostic, and molecular analysis using polymerase chain reaction targeting the 16S rRNA gene confirmed infection with Rhodococcus spp. The patient received targeted antimicrobial therapy with subsequent clinical improvement. This case supports considering Rhodococcus equi as a potential etiologic agent in persistent or relapsing granulomatous skin lesions, regardless of immune status, and demonstrates the utility of molecular diagnostics when conventional histopathologic assessment and culture-based methods fail to establish a definitive diagnosis.