Overlapping mycoses in a case of Seborrheic dermatitis with coexistent Malassezia folliculitis

Seborrheic dermatitis (SD) is a chronic inflammatory skin condition likely caused by several factors, including overgrowth of the lipophilic yeast Malassezia, increased sebaceous gland activity, and a potential genetic predisposition, whereas Malassezia folliculitis (MF) is a fungal infection of hair follicles. In this case, a 22-year-old male initially presented with erythematous papules on the malar region and was clinically diagnosed with SD. Following partial improvement with topical and oral antifungals, the patient developed new pustular lesions involving the malar and chin regions, raising suspicion of MF. The absence of comedones and cysts helped rule out Acne vulgaris. Potassium hydroxide mount from pustular swabs revealed numerous fungal spores, prompting further investigation. Culture on modified Leeming and Notman agar yielded yeast colonies, which appeared as budding yeast cells under light and fluorescence microscopy with Calcofluor white stain. Molecular identification using PCR for the ITS regions and RFLP analysis confirmed the isolate as Malassezia furfur. This case highlights the clinical progression from SD to MF, underscoring the pathogenic potential of Malassezia and the importance of integrating clinical, microscopic, and culture-based molecular diagnostic approaches for accurate diagnosis and targeted treatment in dermatological mycoses.