Pityriasis Versicolor: KOH Examination and Diagnosis

Diagnosis: Pityriasis Versicolor

A 22-year-old male presenting with hypopigmented and hyperpigmented macules and fine scaling on the chest and upper back, confirmed by KOH examination.

Clinical Presentation

Multiple well-demarcated, round to oval macules and patches with fine overlying scale on the upper trunk, shoulders, and proximal upper arms. Lesions are hypopigmented on tanned skin. Besnier sign positive. Wood lamp shows yellow-green fluorescence.

Clinical History

Recurrent episodes each summer for the past 3 years. Works as a lifeguard with significant sun exposure and perspiration. Previous treatment with OTC selenium sulfide shampoo provided temporary improvement.

Treatment

KOH examination demonstrated characteristic spaghetti and meatballs pattern. Ketoconazole 2% shampoo used as body wash daily for 2 weeks then weekly maintenance. Oral fluconazole 300mg once weekly for 2 weeks for extensive disease.

Differential Diagnosis

• Vitiligo • Pityriasis alba • Post-inflammatory hypopigmentation • Tinea corporis • Seborrheic dermatitis • Confluent and reticulated papillomatosis • Secondary syphilis

Key Learnings

• Caused by Malassezia yeast (dimorphic: yeast → mycelial/hyphal form in disease state) • "Spaghetti and meatballs" on KOH: short hyphae with round spores — pathognomonic • Color varies: hypo- or hyperpigmented patches depending on skin tone and sun exposure • Hypopigmentation mechanism: azelaic acid produced by Malassezia inhibits tyrosinase • High recurrence rate — maintenance therapy recommended • Wood lamp: yellow-gold fluorescence • Not truly contagious — Malassezia is part of normal skin flora; overgrowth is the issue • Risk factors: heat, humidity, oily skin, immunosuppression

Tags: fungal, Malassezia, KOH, hypopigmentation, superficial mycosis