Pityriasis versicolor is a common skin complaint in which flaky discoloured patches appear mainly on the chest and back. It is sometimes called tinea versicolor, although the term 'tinea' should strictly refer to infection with a dermatophyte fungus. It is caused by the proliferation of the lipophilic yeast, Malassezia furfur (called Pityrosporum orbiculare in its yeast-like form) which is part of the normal flora of human skin. Usually Malassezia spp. grow sparsely in the seborrhoeic areas (scalp, face and chest) without causing a rash. Nine different species of Malassezia spp have been identified. The most common species cultured from pityriasis versicolor patches is M. globosa.¹

Epidemiology

• Pityriasis versicolor can occur at any age but occurs mainly during adolescence, when the sebaceous glands are more active.²
• Relatively common in hot, humid climates and mainly seen in the UK during spells of hot humid weather.
• Pityriasis versicolor is more common in those with hyperhidrosis (sweat heavily).

Presentation

• Macular lesions of altered pigmentation are seen primarily on the trunk and proximal parts of the limbs and are uncommon on other parts of the body.
• There is a superficial scale which is best seen by scraping the surface with a finger nail.
• In untanned white caucasians, the lesion is hyperpigmented and pink or coppery brown giving a dappled appearance. In darker skins or heavily tanned people, the lesion shows depigmentation (known as pityriasis versicolor alba and is less likely to itch).
  
  
  

  
  

  
  
  
  
• Sometimes the patches start scaly and brown, and then resolve through a non-scaly and white stage.
• Itching, if present, is mild.

Differential diagnosis³

• Vitiligo
• Pityriasis alba
• Tinea corporis
• Seborrhoeic dermatitis
• Pityriasis rosea
• Guttate psoriasis
• Nummular eczema
• Secondary syphilis
• Mycosis fungoides

Investigations

• Yellow to yellow-green fluorescence may be observed on examination of affected areas with a Wood's light.
• Samples of skin scale can be used to confirm the diagnosis; they have a 'spaghetti and meatball' appearance on potassium hydroxide wet-mount examination.
• It is easier to demonstrate the yeasts in scrapings taken from the brown type of pityriasis versicolor than from the white type.
• Microscopy is reported as positive if hyphae and yeast cells are seen. However, culture is often negative because it is quite difficult to grow the yeasts in a laboratory.
• There is no benefit of fungal culture as the organism is part of the normal flora and isolation is therefore not necessarily relevant.

Management

• Pityriasis versicolor should be treated initially with topical antifungals, especially topical imidazoles, e.g. clotrimazole, miconazole, econazole and ketoconazole in various formulations (creams or shampoos). Ketoconazole shampoo or selenium sulphide shampoo are often used as shampoos can cover large areas more easily than creams. One method of applications is to apply the shampoo to wet skin and leave it on for 10 minutes, with the treatment repeated daily for 10 days.⁴
• Patients with extensive or persistent pityriasis versicolor may be prescribed oral treatment (ketoconazole, itraconazole or fluconazole).⁵
• Ultraviolet therapy, to induce maturation of existent melanosomes and accelerate repigmentation, is effective as a second line treatment for severely affected patients. However, depigmented lesions are difficult to improve by ultraviolet therapy.⁶
• Antifungal treatment should be repeated when the scaly component of pityriasis versicolor recurs.
• Oral antifungal treatment may be prescribed for one to three days each month as a preventative in those who have frequent recurrences.

Complications

• Infection often leads to hypopigmentation of the skin, which may persist for months after successful treatment.
• Hypopigmentation will not clear until the skin becomes tanned again, but if the rash is not scaly when scratched, then the infection can be considered as cleared.

Prognosis

• Pink or brown types of pityriasis versicolor generally clear satisfactorily with treatment but the rash often recurs.
• The pale type of pityriasis versicolor also generally clears up with treatment and the skin eventually tans normally with sun exposure.
• White marks are occasionally permanent and resistant to antifungal treatment.