Tinea Versicolor (Pityriasis Versicolor) | Figure 4.21
A: Pityriasis versicolor
(Courtesy of Dr. Paul Getz)
B: Tinea nigra
(Courtesy of Dr. Marcus
Henrique de Sousa Brito
Xavier, Brazil)
C: Piedra
(Courtesy of Doctor Fungus,
www.doctorfungus.org) |
(Figure 4.21A) - Malassezia furfur (yeast form: Pityrosporum ovale or P. orbiculare)
- Yeast part of normal cutaneous flora, but pathogenic when transforms into mycelial form; requires lipid enrichment when growing
- M. furfur produces azelaic acid (a dicarboxylic acid) → blocks melanin synthesis causing ↓ pigmentation
- Presents as hyper- and hypopigmented macules and patches with fine scale in lipid-rich areas of skin; common in summer; facial lesions common in infants
- KOH: “ziti and meatballs” (short, thick hyphae with grape-like spores); culture requires lipid enrichment (olive oil overlay); Wood’s light shows pale yellow fluorescence
- Treatment: topical imidazoles, selenium sulfide, zinc pyrithione, or oral ketoconazole 400 mg qweek × 2 doses
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