Definition

Pityriasis rosea is a self-limiting skin condition characterized by an initial “herald patch,” followed by a symmetrical rash of smaller scaly oval lesions, typically distributed along the trunk in a “Christmas tree” pattern. It primarily affects young adults, resolves within 6–10 weeks, and may be associated with a viral trigger, though its exact cause is unknown.

Epidemiology

This condition is most prevalent in healthy individuals aged 10–35, with a slight female predominance. Although it can occur in any season, some studies suggest increased incidence in spring, fall, or winter, depending on geographic location. It affects approximately 0.5% to 2% of the population worldwide and is rarely seen in children under two years old.

Etiology

The exact cause of pityriasis rosea remains uncertain. A viral origin is widely hypothesized, with human herpesvirus types 6 and 7 (HHV-6/7) being the most strongly associated, though evidence is inconclusive. Other possible triggers include H1N1 influenza, SARS-CoV-2, and certain vaccines, such as COVID-19, smallpox, and hepatitis B. Drug-induced cases have also been reported, linked to medications like ACE inhibitors, NSAIDs, and antipsychotics.

Clinical Features

The hallmark of pityriasis rosea is the herald patch, which is a slightly raised, salmon-pink or red lesion 2–5 cm in diameter with a collarette of scaling at the margin. This is followed by the secondary rash, which appears as smaller oval plaques with similar scaling, distributed primarily on the trunk and upper extremities typically distributed along Langer lines in a “Christmas tree” pattern. The rash often spares the face, palms, and soles. In some cases, prodromal symptoms such as mild fever, headache, or malaise precede the rash. About 25% of patients experience pruritus, ranging from mild to severe.

Variants of the condition may involve atypical features, including inverse patterns affecting the axillae or groin, or more severe forms with pustules, vesicles, or purpuric lesions.

Diagnosis

Diagnosis is primarily clinical, based on the characteristic appearance and distribution of lesions. When uncertain, histology may confirm subacute dermatitis, particularly for drug-induced cases. It is essential to differentiate pityriasis rosea from other conditions, especially when atypical lesions or palm/sole involvement occurs.

Management

Treatment focuses on symptom control and patient reassurance, as the condition is self-resolving. Common interventions include:

General measures: Using moisturizers, gentle bathing practices, and limited sun exposure.
Topical treatments: Low to Medium-strength corticosteroids and antipruritic lotions to alleviate itching.
Systemic treatments: Oral antihistamines for itching; acyclovir for faster lesion resolution in severe cases; and, in rare instances, oral corticosteroids or phototherapy.

For pregnant women, caution is advised as pityriasis rosea may increase the risk of miscarriage during the first trimester if associated with active HHV-6 infection.

Written by:

Raneem Alahmadi, Medical Intern

Revised by:

Naif Alshehri, Medical Intern

Resources:

Bolognia 5th edition

Dermnet