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Pityriasis versicolor

BMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h1394 (Published 07 April 2015) Cite this as: BMJ 2015;350:h1394
  1. Sruthi Renati1,
  2. Anthony Cukras2,
  3. Michael Bigby2
  1. 1Harvard Medical School, Boston, Massachusetts, USA
  2. 2Department of Dermatology, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, MA 02215, USA
  1. Correspondence to: M Bigby mbigby{at}bidmc.harvard.edu

The bottom line

  • Pityriasis versicolor is a superficial fungal infection of the skin caused by Malassezia species that induces a characteristic rash of well demarcated, thin, scaly plaques that can be hypopigmented, hyperpigmented, or erythematous

  • Diagnosis is usually made clinically, based on characteristic skin lesions and the “evoked scale sign” (when stretching or scraping the skin makes the fine scale of lesions more apparent)

  • Diagnosis is aided by microscopic examination of potassium hydroxide treated or stained skin scrapings, which reveal numerous spores and hyphae

  • First line topical treatments include ketoconazole, selenium sulphide, or zinc pyrithione shampoo. Systemic treatment is limited to use in extensive disease

  • Disease recurrence is common; options for prophylaxis include topical ketoconazole, selenium sulphide, or zinc pyrithione shampoo

What is pityriasis versicolor?

Pityriasis versicolor is a superficial fungal infection of the skin. It is caused by Malassezia, a lipophilic dimorphic fungus. This fungus is part of the normal skin flora but can cause disease when it converts to its pathogenic hyphal form. Certain environmental, genetic, and immunological factors can predispose to this pathogenic conversion and contribute to the development of disease.

The fungus grows best in warm and humid conditions, explaining the higher prevalence of pityriasis versicolor in humid tropical climates. A survey in central Sweden found a 0.5% prevalence of pityriasis versicolor, whereas the prevalence is as high as 50% in tropical countries.1 2 There is a significant increase in disease prevalence between childhood and adolescence, probably due to hormonal changes that increase sebum production and allow for a more lipid-rich environment in which the fungus can grow. The disease is also more common among adolescents and young adults who are physically active.3 Although effective oral and topical treatment options exist, disease recurrence is common and pityriasis versicolor can have an impact on quality of life.4

How does pityriasis versicolor present?

Patients with pityriasis …

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