A Case of Staphylococcus simulans Colonization in a Patient with Psoriasis

A 20-year-old female patient presented with localized erythematous scaly lichenified plaques on her right lower leg. Despite traditional treatments, the lesions consistently recurred in previously affected anatomical locations. Bacterial culture was performed, and Staphylococcus simulans was identified on both lesional and nonlesional skin. Histopathological examination revealed parakeratosis, Munro microabscess, hypogranulosis and regular acanthosis with an elongated rete. Based on clinical and histological findings, the patient was finally diagnosed with possible psoriasis. Although S. simulans is a common livestock colonizer, it rarely colonizes human skin. Herein, we report the first case of S. simulans colonization in a recurrent psoriatic lesion in previously affected anatomical locations.