Case

A 12 year old girl presents with a two week history of a scaly rash on her trunk. There is minimal itching and she was treated for tinea corporis 3 weeks ago. How would you evaluate this young girl?

Pityriasis rosea is a common skin rash that has the highest incidence in young adults. There is equal incidence in boys and girls and there is a higher incidence in fall and early winter. 

Etiology

1. Although there is no known cause, a viral etiology has been proposed because of its occurrence in epidemics and intrafamilial spread. No organism has been isolated.

1. There are no constitutional symptoms and there aren't any extracutaneous manifestations. There are no prodromal symptoms.
2. In about 85% of cases, the first lesion is the "herald patch" or "mother patch". This is found most commonly on the trunk or neck region. It may range in size form 1-10 centimeters and is initially an oval macular or maculopapular lesion. This then develops into a scaly lesion with central clearing. It is often misdiagnosed as tinea corporis.
3. About 10 days later, crops of oval macular or maculopapular lesions appear on the trunk, neck, and proximal extremities. The lesions are usually aligned parallel to the ribs and form a "Christmas tree" distribution. The initially pink lesions become red and eventually develop fine scales. 
4. Pruritis is minimal
5. The lesions may come out for two weeks, stay for two weeks, and fade for two weeks. After lesions disappear there may be temporary post inflammatory hypo or hyper pigmented areas that will fade.
6. May be less common variations with urticarial lesions, purpura, and vesicles. May rarely involve the palms, soles, and mucous membranes. 

1. This is a clinical diagnosis and must be differentiated from secondary syphilis, tinea versicolor, psoriasis, and drug reactions.
2. Think of pityriasis rosea when you see an older child with an extensive rash and the child is relatively asymptomatic.

1. Symptomatic with moisturizers and anti-pruritic therapy
2. Rarely require topical steroids.
3. REASSURANCE

1. Bloomfield, Diane. Pityriasis Rosea. Pediatrics in Review. April 1994.
2. Ginsburg, Charles. Pityriasis Rosea. Pediatrics Infectious Disease Journal. November 1991.
3. Hartley AH. Pityriasis Rosea. Pediatrics in Review. 1999; 20:266-270.
4. Amer A. et al.  The Natural History of Pityriasis Roseas in Black American Children.  Arch Pediatr Adolesc Med Vol 161 May 2007