## Tinea Versicolor: Etiology and Microscopy **Key Point:** Tinea versicolor (pityriasis versicolor) is a superficial fungal infection caused by **Malassezia furfur** (formerly Pityrosporum orbiculare), a lipophilic yeast that is part of normal skin flora but becomes pathogenic under certain conditions. ### Malassezia furfur — Organism Characteristics - **Lipophilic yeast:** requires lipids for growth; thrives in sebaceous areas - **Dimorphic:** exists as yeast (round/oval) and mycelial (filamentous) forms - **Normal flora:** colonizes skin in 90% of healthy individuals; pathogenic overgrowth occurs with heat, humidity, immunosuppression, or genetic predisposition ### Microscopic Findings on KOH Mount **High-Yield:** The pathognomonic finding is the **'spaghetti and meatballs' appearance**: - **Spaghetti** = short, thick hyphae or mycelial elements - **Meatballs** = round/oval yeast cells - Both forms present simultaneously in the same preparation | Organism | KOH Mount Finding | Clinical Condition | | --- | --- | --- | | **Malassezia furfur** | **'Spaghetti and meatballs'** | **Tinea versicolor** | | Candida albicans | Pseudohyphae + budding yeast | Candidiasis | | Cryptococcus neoformans | Encapsulated yeast (India ink) | Cryptococcal meningitis | | Aspergillus fumigatus | Septate hyphae, acute angle branching | Aspergillosis | **Clinical Pearl:** Tinea versicolor presents as **hypo- or hyperpigmented macules** (often on trunk and proximal limbs) due to interference with melanin synthesis by Malassezia metabolites. The lesions do not fluoresce under Wood's lamp (unlike the older name 'pityriasis versicolor' might suggest). **Mnemonic:** **MAL** = **M**alassezia, **A**ppearance = 'spaghetti and **L**ips' (round meatballs). 
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