A Boy With a Scaly, Nonpruritic Rash
A 14-year-old white boy was referred to the allergy clinic by his pediatrician for the evaluation of what were thought to be hives. The patient has a history of atopic dermatitis, and he recently had completed a 5-year course of allergen immunotherapy.
He presented with a scaly, nonpruritic rash mainly on his trunk, which had been present for the previous 4 weeks. Daily oral antihistamines taken for the previous 2 weeks had not improved the rash.
What is the cause of these nonpruritic lesions?
(Answer and discussion on next page)
Answer: The boy has pityriasis rosea
Pityriasis rosea is a benign, self-limited condition that typically occurs in older children, adolescents, and young adults. While most patients are asymptomatic, some patients may report prodromal symptoms or may experience pruritus.
Figure:The long axis orientation of the oval shaped lesions of pityriasis rosea tends to follow skin cleavage lines, creating a distinct “Christmas tree” pattern, as was seen on the torso of this 14-year-old boy.
In approximately 70% of cases, a “herald patch” is the initial clinical sign. This initial solitary lesion is a sharply defined, oval, scaly plaque with erythematous, slightly raised edges.1 Within 2 to 3 weeks, the rash progresses with the development of similar but smaller lesions that typically spread over the torso and proximal extremities, as was observed in this patient. The long axis of the oval lesions tends to follow skin cleavage lines (Langer lines), creating a distinct “Christmas tree” pattern. An inverse distribution with lesions appearing more prominently over the patient’s scalp, face, and groin, may occur in younger children.2
Although the cause of pityriasis rosea is not definitively known, a viral etiology has been suggested, possibly the reactivation of human herpesvirus 6 and/or human herpesvirus 7.3
The diagnosis of pityriasis rosea usually is made clinically based on the patient’s history and the characteristic physical examination findings. If the diagnosis of pityriasis rosea is not clearly evident, one might consider tinea corporis, nummular eczema, guttate psoriasis, and secondary syphilis infection in the differential diagnosis.
While urticaria can occur at any age and can vary in location, size, and appearance, individual urticarial lesions typically last less than 24 hours, are extremely pruritic, and improve significantly with administration of oral antihistamines. Unlike tinea corporis lesions, which typically have central clearing, pityriasis rosea lesions have central scaling.
Because pityriasis rosea typically is asymptomatic (aside from the characteristic rash) and self-limiting, reassurance and observation are the usual recommendations. In the case presented here, the patient’s symptoms had completely resolved in the 2 weeks after he presented to the allergy clinic.
For patients who are experiencing pruritus, supportive care with calamine lotion, topical corticosteroids, and/or oral antihistamines can provide relief. Other therapeutic options that have been described include sunlight exposure, oral macrolide antibiotics, and oral acyclovir.4
1. Browning JC. An update on pityriasis rosea and other similar childhood exanthems. Curr Opin Pediatr. 2009;21(4):481-485.
2. Trager JDK. What’s your diagnosis? Scaly pubic plaques in a 2-year-old girl—or an “inverse” rash. J Pediatr Adolesc Gynecol. 2007;20(2):109-111.
3. Drago F, Broccolo F, Rebora A. Pityriasis rosea: an update with a critical appraisal of its possible herpesviral etiology. J Am Acad Dermatol. 2009;61(2):303-318.
4. Zawar V. Sudden onset of generalized scaly eruptions. J Fam Pract. 2012;61(9):557-559.
Dr Ocampo is a pediatrician at the 35th Medical Group Pediatrics Clinic, Misawa Air Base, Japan. Dr Waibel is an allergist/immunologist at San Antonio Military Medical Center, Fort Sam Houston, Texas. The opinions or assertions herein are the private views of the authors and are not to be construed as reflecting the views of the Department of the Army, the Department of the Air Force, or the Department of Defense.
Kirk Barber, MD, FRCPC––Series Editor:Dr Barber is a consultant dermatologist at Alberta Children’s Hospital and clinical associate professor of medicine and community health sciences at the University of Calgary in Alberta.