Pityriasis Rosea

Definition/diagnostic criteria Pityriasis rosea is a self-limiting papulosquamous disorder characterised primarily by an initial herald patch, followed by subsequent smaller, salmon-pink patches on the trunk and extremities. The diagnosis is predominantly clinical, relying on characteristic skin findings and a typical evolution pattern.

Epidemiology Pityriasis rosea has a worldwide distribution, affecting individuals of all races but the exact prevalence in the UK is not well documented. It is more commonly diagnosed in spring and autumn. The disease is most prevalent in the 10-35 age group, but it can affect individuals of any age.

Diagnosis
Clinical features: The condition commences with a ‘herald patch’, a single, 2-10 cm oval pink plaque with a fine scale, typically located on the trunk. After 1-2 weeks, numerous smaller patches appear on the trunk and limbs in a ‘Christmas tree’ pattern, following the lines of skin cleavage. In darker skin types, the herald patch may be hyperpigmented, and the subsequent lesions can present with a range of colours from pink to dark brown or violet. The rash is frequently accompanied by mild itching. Mucous membranes, palms, soles, and the face are usually spared.

Investigations: Pityriasis Rosea is generally a clinical diagnosis and does not necessitate routine investigations.

Treatment Treatment is mainly supportive, focusing on relieving symptoms.

• Topical steroids and oral antihistamines can be used to manage itching.
• Emollients can also be beneficial in alleviating discomfort.

Prognosis Pityriasis Rosea typically resolves without treatment within 2-12 weeks, although it can persist for longer. The prognosis is excellent, and recurrences are rare. Post-inflammatory hyperpigmentation or hypopigmentation can occur, particularly in individuals with darker skin, but these are usually transient. No long-term sequelae are associated with the condition.