- Clinical science
Pityriasis rosea is a self-limiting rash commonly affecting young adults, especially females. The etiology is mostly unknown, although it is thought to be caused by a 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 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 is suspected based on the following:
- Pityriasis rosea can occur in clusters, affecting many people living in the same community.
- Seasonal variations (more common in the spring and fall)
- Preceded by a prodromal flu-like illness in some patients
- Ampicillin can worsen the rash distribution
- Immunological evidence (lack of B-cell activity)
- Life-long immunity (recurrence is rare but possible)
- 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)
- In children: The classic distribution of the rash is not seen. The lesions involve the scalp, face, hand and feet, while sparing the trunk (an inverse distribution). In some children, the rash primarily affects the groin and axillary regions.
- 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)