Unusual Presentation of Superficial Dermatophyte Infections

Dermatophytosis, commonly referred to as ringworm or tinea, is a fungal infection affecting the skin, hair, or nails, primarily caused by the genera Trichophyton , Epidermophyton , and Microsporum. These infections typically present as erythematous, scaly papules that progress to annular plaques. However, atypical presentations can occur, particularly in immunocompromised patients. This case report details a 65-year-old male with rheumatoid arthritis who developed multiple dark-colored lesions, pustules, and ulcers on his skin and oral mucosa over 2 weeks. Initial KOH preparations were negative, raising concerns about methotrexate-induced toxicity. A skin biopsy ultimately revealed PAS-positive fungal hyphae, confirming a diagnosis of tinea corporis. This case underscores the importance of recognizing atypical dermatophytic infections in immunocompromised individuals, highlighting the potential for unusual presentations such as erosions and pustules, which deviate from classic annular scaly plaques. It emphasizes the necessity of histopathological confirmation in diagnosing dermatophyte infections, especially when KOH preparations yield negative results.