Pityriasis Versicolor

PITYRIASIS VERSICOLOR

Causative Organism

• Caused by yeast-like micro-organism Pityrosporum ovale (orbiculare) or Malessezia furfur
•  Becomes pathogenic when its growth is encouraged by increased sebum secretion or depressed immunity

 Skin Lesion Morphology

Pale, scaling hypopigmented macules develop over the skin of the chest and back in young adults 

• Fine velvety scales that are not visible but are seen by scraping the lesion.
• Central upper trunk the most frequent site.
• Microscopy: grape-like clusters of spores and a meshwork of pseudomycelium in skin scrapings
• made more transparent by soaking the scales for 20 minutes in 20 per cent potassium hydroxide.

Skin surface biopsy

• Permanent preparation made using cyanoacrylate adhesive to remove a strip of superficial stratum corneum from the skin surface on a glass slide
• The slide is ‘rolled off’ the skin after 20 seconds and then stained with periodic acid- Schiff reagent
• The skin patches often fluoresce an apple green in long-wave UVR (Wood’s light).

Treatment

• Topical imidazole creams (e.g. miconazole, clotrimazole, econazole) for 6 weeks or
• Ketoconazole shampoo to wash the affected areas once daily for 5 days

Exam Question

• The skin patches often fluoresce an apple green in long-wave UVR (Wood’s light).
• Ketoconazole shampoo to wash the affected areas once daily for 5 days
• Caused by yeast-like micro-organism Pityrosporum ovale (orbiculare) or Malessezia furfur