Pityriasis Versicolor

Question 1

Aetiology of PV.

Answer 1

Caused by overgrowth of Malassezia yeast, which is a normal commensal organism on human skin.

Question 2

Factors that promote the conversion of Malassezia from yeast to its pathogenic mycelial form.

Answer 2

> Hot and humid climates.
Increased sweating.
Oily skin.
Immunosuppression.

Question 3

Pathophysiology of PV.

Answer 3

Malassezia yeast resides in the stratum corneum (outermost layer) and converts to its pathogenic mycelial form under favourable conditions.

The mycelial form produces dicarboxylic acids, such as azeleic acid, which inhibits melanin production in melanocytes. This leads to hypopigmented lesions.

Hyperpigmentation may result from an inflammatory response or increased melanin production in unaffected areas.

Infection remains confined to the stratum corneum without deeper invasion.

Question 4

Where is PV most common?

Answer 4

Tropical and subtropical regions.

Question 5

Clinical features of PV.

Answer 5

Hypopigmented or hyperpigmented macules/patches with fine scaling, primarily on trunk, neck, and upper arms. Lesions may coalesce to form larger patches.

Pruritus: mild and not always present.

Seasonal variation: lesions may become more apparent in summer months due to tanning of surrounding normal skin.

Question 6

Investigations and diagnosis of PV.

Answer 6

Clinical diagnosis.

Wood’s lamp examination: lesions may fluoresce.

Microscopy: skin scrapings from the lesions can be examined using KOH preparation. This may reveal a characteristic ‘spaghetti and meatball’ appearance of hyphae and spores.

Fungal culture: rarely performed as it is time-consuming and not usually necessary for diagnosis.

Question 7

PV differentials.

Answer 7

> Vitiligo.

> Pityriasis alba.

> Seborrheic dermatitis.

> Erythrasma: caused by Corynebacterium minitissimum, presenting as brownish-red patches, often in intertriginous areas. Wood’s lamp examination shows coral-red fluorescence, aiding differentiation.

Question 8

Management of PV.

Answer 8

First-line:
Topical antifungal, such as: ketoconazole shampoo (used as bodywash): apply daily for 5-7 days.

Selenium sulfide 2.5% lotion: applied to affected areas for 10 minutes daily for 1 week.

Clotrimazole cream: applied twice daily for 2-4 weeks.

Second-line:
Oral antifungal, such as:

itraconazole: 200mg daily for 7 days.

Fluconazole: 300mg once weekly for 2 weeks.

Monitor for side effects, especially with oral antifungals (can have hepatic implications).

Maintenance Therapy:
Recurrence is common. Monthly use of topical antifungals can help prevent relapse, especially in hot and humid climates.