Pityriasis VersicolorEdit

Pityriasis versicolor, also known as tinea versicolor, is a common superficial fungal infection of the skin caused by yeasts of the genus Malassezia. The condition presents as hypo- or hyperpigmented macules and patches, most frequently on the trunk and proximal limbs, that may become more noticeable after sun exposure. Although unsightly for some patients, pityriasis versicolor is not dangerous and is not considered contagious. The disease tends to occur in warm, humid climates and can affect children, adolescents, and adults.

Causes and pathogenesis

Pityriasis versicolor stems from colonization of the stratum corneum by Malassezia species, most often the Malassezia furfur complex. These lipophilic yeasts are part of the normal skin microbiome and can overgrow in favorable conditions. When Malassezia metabolizes skin lipids, it produces acidic byproducts such as azelaic and other fatty acids that can interfere with melanocyte function, leading to pigment disturbances in the affected areas. The precise reasons why overgrowth occurs in some individuals but not others remain incompletely understood, but factors such as climate, skin oiliness, and personal susceptibility appear to play a role.

Relevant agents and concepts include Malassezia species, the skin’s lipid milieu, and the role of pigment synthesis disruption in melanocytes.
Conditions that can predispose to or accompany pityriasis versicolor include warm, humid environments, excessive sweating, oily skin, and, in some cases, immunosuppression.

Epidemiology

Pityriasis versicolor is widely distributed and can occur worldwide, with higher incidence in tropical and subtropical regions. It is most common in adolescents and young adults, though it can affect people of any age. The condition is recurrent rather than typically fatal, and individuals may experience multiple relapses over years.

For background on the organisms involved, see Malassezia and related literature on superficial fungal skin infections.

Clinical features

The hallmark of pityriasis versicolor is the presence of pale, tan-to-brown or pinkish-to-silvery macules and patches on sun-exposed areas of the trunk, shoulders, and upper arms. Lesions may be hypo- or hyperpigmented and often have fine scale that becomes more evident with skin irritation or sun exposure. Itching is usually mild or absent. Lesions may wax and wane with seasons and changes in humidity.

The condition is typically asymmetric and more conspicuous after tanning, when pigment contrasts with surrounding skin are most noticeable.

Diagnosis

Diagnosis is usually clinical, supported by bedside tests.

Wood’s lamp examination can reveal characteristic fluorescence of affected skin in some cases, aiding visualization of subtle lesions.
Microscopic examination of skin scrapings treated with potassium hydroxide (KOH) commonly shows short hyphae with arthroconidia—the so-called “spaghetti and meatballs” appearance—confirming fungal involvement.
Culture is rarely necessary but can be used in uncertain cases or research settings. For more on laboratory techniques, see KOH preparation and Wood’s lamp.

Differential diagnosis

Other conditions that can resemble pityriasis versicolor include vitiligo, pityriasis rosea, postinflammatory hypopigmentation, seborrheic dermatitis, and certain fungal infections caused by dermatophytes. Distinguishing features include pigment distribution, scaling, patient history, and laboratory findings.

Treatment

Treatment aims to eradicate Malassezia in the skin and address pigment changes. Most cases respond to topical antifungal therapies, and systemic treatment is reserved for extensive or recurrent disease.

Topical antifungals commonly used include selenium sulfide preparations, zinc pyrithione, and azoles such as ketoconazole or itraconazole.
For more extensive disease or recurrences, short courses of oral antifungals such as fluconazole, itraconazole, or ketoconazole may be used under medical supervision.
Adjunctive skin care, avoiding occlusive oily products, and sun protection can help reduce cosmetic differences while pigment normalizes.
Maintenance strategies and the choice between intermittent topical therapy versus periodic systemic therapy are topics of clinical discussion, given recurrence rates.

Prognosis and recurrence

Pityriasis versicolor generally has a good prognosis with appropriate treatment, but recurrence is common. Relapses can occur months to years after an initial episode, particularly in individuals living in hot and humid climates or those with ongoing risk factors such as oily skin or persistent exposure to heat and sweating. Maintenance regimens and prompt retreatment upon relapse are common strategies.

Controversies and debates

Within dermatology, debates surround optimal management to minimize relapses, especially in individuals with frequent recurrences. Points of discussion include: - The balance between topical maintenance therapy and intermittent systemic antifungals, considering potential adverse effects and patient adherence. - The risk-benefit profile of long-term topical ketoconazole or oral azoles, given concerns about liver effects with systemic use and the potential for drug interactions. - Nonpharmacologic strategies, such as climate-adapted skin care and sun exposure, versus reliance on antifungal agents, and how best to tailor approaches to individual patients. - The role of routine laboratory testing or imaging in ambiguous cases, given that pityriasis versicolor is usually diagnosed clinically with supportive microscopy.