Pityriasis versicolor

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 fungus of the genus Malassezia (formerly known as Pityrosporum) 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. However the fungus may change from its normal form to a pathological mycelial form.

Pathogenic forms may be triggered by various factors, including humidity and high temperature, hyperhidrosis, familial susceptibility, and immunosuppression. The most common Malassezia species associated with pityriasis versicolor is M. globosa, with M. sympodialis and M. furfur also frequently seen¹.

Epidemiology²

• It occurs worldwide but is most common in hot and humid climates. It occurs more often in the summer than in the winter months in temperate zones.

• Prevalence may be up to 40% in some tropical countries compared with less than 1% in temperate climates.

• Most often it affects teenagers and young adults. It is less common in infants and the elderly..

Most infections occur in normal healthy people but the following factors increase the risk:

• Hyperhidrosis or increased physical activity causing sweating.

• Occlusive clothes, dressings or ointments.

• Immunosuppression or immune deficiency.

• Malnutrition.

Presentation

• It usually has an insidious onset and in some cases it can be several months before it is noticed.

• Macular lesions and patches of altered pigmentation are seen primarily on the trunk.

• These lesions frequently spread to the neck, upper arms and abdomen and can sometimes occur at other sites. The rash is usually seen in sebum-rich sites. The face may be affected in some.

• There is a superficial scale which is best seen by stretching the affected skin, or scraping the surface.

Pityriasis versicolor close-up

By Richardkiwi at nl.wikipedia (Own work), Public domain, via Wikimedia Commons

Pityriasis versicolor on the forehead

By Grook Da Oger (Own work) CC BY-SA 3.0, via Wikimedia Commons

• Sometimes the patches start scaly and brown and then resolve through a non-scaly and white stage.

• Itching, if present, is mild.

• Pityriasis versicolor is not contagious, as it is a commensal yeast.

Differential diagnosis

• Vitiligo.

• Pityriasis alba.

• Tinea corporis.

• Seborrhoeic dermatitis (may co-exist).

• Pityriasis rosea.

• Guttate psoriasis.

• Discoid (nummular) eczema.

• Secondary syphilis.

• Mycosis fungoides.

Investigations

Investigations are not usually necessary, as the diagnosis is often made clinically. They may be necessary if the condition is not responding to treatment or if the diagnosis is unclear. Where required, skin scrapings can be sent for microscopy. The spores and hyphae have a 'spaghetti and meatball' appearance on potassium hydroxide wet-mount examination. Yellow to yellow-green fluorescence may be observed on examination of affected areas with a Wood's light. There is no benefit of fungal culture, as the organism is part of the normal flora and isolation is therefore not necessarily relevant.

Management²³

• Pityriasis versicolor should be treated initially with topical antifungals, especially topical imidazoles - eg, clotrimazole, miconazole, econazole and ketoconazole in various formulations (creams or shampoos).

• Ketoconazole shampoo (Nizoral®) is usually first-line and should be applied on to affected areas and made into a lather; it should then be left for three to five minutes before washing off. This should be repeated daily for five days⁴.

• Selenium shampoo can be used as an alternative (its use is unlicensed). It should be diluted with water (to reduce the likelihood of irritation), applied to affected areas for ten minutes and then rinsed off. This should be repeated daily for seven to ten days. This is contra-indicated in pregnancy.

• If very small areas are involved, or in pregnancy, antifungal imidazole creams such as clotrimazole may be used as an alternative. The cream should be applied twice a day for two to three weeks.

• In widespread or resistant cases, prescribe itraconazole 200 mg daily for seven days (although terbinafine is active against dermatophytes (eg, tinea), it actually has little effect on yeast infections). Alternatively, fluconazole may be used - 50 mg daily for two to four weeks, or 300-400 mg weekly for one to three weeks.

• Patients should be advised that it can take several months for the skin colour to return to normal.

• Antifungal treatment should be repeated when the scaly component of pityriasis versicolor recurs.

• Recurrences of pityriasis versicolor are common.
  

Prophylaxis

• For those who are prone to develop recurrent episodes in the sun, they can be advised to use ketoconazole shampoo prophylactically once a day for three days prior to their sun exposure.

• Ketoconazole or selenium sulfide shampoo may be applied for five to ten minutes one to four times monthly for those who have frequent recurrences.

• Oral antifungal treatment may occasionally be prescribed monthly as a preventative measure in those who have frequent recurrences (eg, fluconazole 300 mg per month).

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; however, 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.