Classic herald patch, the "mother," on the left shoulder, with secondary lesions, the "babies," scattered around on the back.
Classic herald patch, the "mother," on the left shoulder, with secondary lesions, the "babies," scattered around on the back.
Pityriasis rosea (PR) is a common, benign, self-limited papulosquamous skin condition affecting primarily children and young adults. Seventy-five percent of patients are from 10 to 35 years of age.
There is no internal involvement. It is somewhat more common in the winter. Most cases occur in isolation, but occasionally there will be two family members affected. Various drugs have been reported to have caused a PR-like eruption, but it is highly unlikely that a drug can cause the classic presentation of a herald patch followed by secondary lesions.
Probably. Why?
Before the pandemic, there was some speculation that the cause of PR might be a “reactivated” virus and that human herpesviruses 6 and 7 were to blame. Many people become infected at an early age with these two viruses-—both can cause roseola, a childhood skin rash--which then stay in the body. However, PR’s pandemic-related behavior weakened that hypothesis. Cases of PR plummeted during the pandemic suggesting that exposure to some (infectious?) agent is the cause of PR. If reactivation of the roseola virus was the cause, then the pandemic with its assocated stress should have led to more cases.
No increased risk of birth complications and spontaneous abortion was found in pregnant patients with pityriasis rosea compared to matched controls. JAAD 2024
In many patients, a herald patch appears first. The herald patch is round to oval, red and scaly, and may be from 2-6 cm in diameter. It typically occurs on the trunk, neck or proximal extremities. When a patient presents with a solitary papulosquamous lesion of short duration, think PR.
One to several weeks later, the patient experiences a diffuse eruption of red, oval plaques on the trunk, axilla, sides of neck and the groin. PR definitely prefers the sun-protected areas and this is a helpful diagnostic sign. The palms and soles are usually spared (as compared to secondary syphilis where they are usually involved). Many of the plaques may be noted to have a collarette of scale which is also a helpful diagnostic sign. Usually, the long axis of the plaques runs parallel to the ribs giving a Christmas tree pattern.
Oral lesions (exanthema) may occur [JAAD 2017;77;833]. Typical are erythematous macules and papules, vesicles and petechiae especially of the palate.
The areas hidden from the sun like the axilla, buttocks and groin are preferrentially affected. For pictures that are NSFW (not safe for work) see here.
Common considerations are guttate psoriasis, secondary syphilis, drug-induced PR-like eruptions and PLEVA. If there is any question that the patient may have secondary syphilis (e.g., no herald patch and the palms and soles are involved), an RPR should be obtained.
PR and PR-like eruptions have occurred after vaccination including Covid-19. Some eruptions are similar to classic PR with a herald patch and prodromal symptoms. Others are PR-like and do not have prodromal symptoms nor a herald patch. The majority of Covid vaccine PR development derived from the first dose of vaccine. Medium time from vaccine to PR onset was 9 ± 6.3 days. Finally, no cases of severe diseases or PR following the third dose of the vaccines have been described.
PR-like eruptions may occur after drugs including captropril, barbiturates, and isotretinoin.
Untreated, PR usually resolves spontaneously within 2-3 months although some cases may last 6 months. In asymptomatic patients, no active treatment is necessary. If itching is a problem, a topical steroid may be helpful.
Drago et al in 2006 [JAAD 2006;54:82] conducted a study of oral acyclovir (800 mg 5/day x 7 days) vs placebo in 87 patients, aged. He found on 2 week follow up, 79% of patients had fully regressed compared with 4% of the placebo group. Unfortunately, his study was neither randomized nor double blinded. Rassai et al in 2001[J Eur Acad Dermatol Venereol. 2011;25:24] conducted a study of low dose acyclovir (400 mg 5day x 7 days) vs no treatment in a randomized, investigator-blinded study of 64 patients. They found resolution of lesions in 78% of acyclovir-treated vs 27% of placebo-treated patients at 2 weeks. Ganguly et al[J Clin Diagn Res. 2014;8:YC01–4] in 2014 conducted a randomized, double-blinded, placebo controlled study of 73 patients with acyclovir 800 mg 5/day for 7 days vs placebo and found resolution of lesions on the 14th day in 87% of treated patients vs 33% of placebo-treated patients. Recently in 2016, Singh et al [Indian J Dermatol Venereol Leprol 2016;82:505] published a smaller study of 27 patients in an randomized, blinded, placebo-controlled trial using acyclovir 800 mg 5/day x 7 days and complete clearing as the endpoint. They found no benefit to the use of acylovir. The number of days to cure was 27 in the placebo group and 33 days in the acyclovir group.
Of all the published studies, that by Ganguly et al is the most robust, being randomized and double blinded. It does support the use of acyclovir in PR. Although the study by Singh et al gives contrary results, it is much smaller in size. It seems reasonable for more severe cases of PR to give acyclovir 800 mg 5/day x 7 days.
Sunlight chases PR lesions away. The patient may expose his/her skin to the sun several times a week (don't burn) or if necessary, receive light therapy (UVB) in the dermatologist's office.
Topical steroids only show modest benefit. For mild to moderate itching, a medium-potency topical steroid may be given (e.g., triamcinolone 0.1% cream).
The patient should be told that if the rash persists beyond 4-6 months, he/she should return for further evaluation. Such cases of "chronic PR" should be biopsied to exclude psoriasis, pityriasis lichenoides or other conditions.
A mother (herald) patch and multiple babies.
Papules coallescing into plaques in the groin.
Notice the linear, parallel structure.
The classic collarette of scale. Notice how the plaque is oriented along the skin lines.
Herald patch.
Herald patch.
Herald patch.
Herald patch.
Herald patch.
Herald patch.
Herald patch.
Homepage | Who is Dr. White? | Privacy Policy | FAQs | Use of Images | Contact Dr. White