- Clinical science
Pityriasis rosea is a self-limiting rash that most commonly affects young adults, especially females. Although the exact etiology is unknown, pityriasis rosea is thought to be triggered by viral infection. The majority of patients present with a solitary, coin-sized herald patch, followed by multiple, oval, scaly papules distributed in a classic Christmas tree pattern on the trunk. Except for mild pruritus, pityriasis rosea is asymptomatic. The lesions typically disappear within two months, often causing postinflammatory hyperpigmentation or hypopigmentation. Typically, only symptomatic treatment of pruritus with lotions, oral antihistamines, and/or a short course of topical steroids is necessary.
- Age range: 10–35 years of age
- Sex: ♀ > ♂ (reason unknown)
Epidemiological data refers to the US, unless otherwise specified.
- A viral etiology (HHV 6 and 7) is suspected based on the following: 
- Prodrome: (1–2 weeks prior to rash onset): flu-like symptoms (e.g., malaise, fever, pharyngitis)
- Initial eruption (∼ 90% of cases): herald patch (mother patch)
- Secondary eruption (2–21 days later)
- Pruritus may occur in 25–75% of cases.
- Postinflammatory hypopigmentation or hyperpigmentation (resolves over several months)
- Spontaneous resolution within 6–8 weeks
- Mild cases
- Severe cases (severe pruritus or widespread rash)