A 7-year-old healthy boy is brought to the dermatology clinic by his parents after having had a 3-week history of a rash. The patient’s rash was slightly pruritic, and it involved predominantly the trunk, starting as one larger pink patch with fine scale and subsequently spreading with smaller similar macules and patches. The boy’s palms and soles were spared of the rash.
Submit your diagnosis to see full explanation.
Pityriasis rosea (PR) is an acute, self-limited dermatosis characterized by oval, erythematous lesions located primarily on the trunk. Robert Willan first described PR in 1798.1 Since then, several other names have been used to describe PR’s clinical presentation, including pityriasis circinata, roseola annulata, and herpes tonsurans maculosus. In 1860, a French dermatologist, Camille Melchior Gilbert, gave PR its current name.2
Pityriasis rosea most commonly affects individuals in late childhood and early adulthood, with the majority of cases occurring between ages 10 and 35.3 PR exhibits some seasonal variation with increased occurrence in colder seasons. The overall prevalence of PR has been estimated to be 1.31%, which is likely an underestimation, as it does not take into account cases diagnosed by nondermatologists and atypical cases that are often misdiagnosed.4
The etiology is thought to be infectious; however, its exact cause remains unknown. Support for an infectious etiology comes from its distinct presentation and clinical course, lack of recurrence, seasonal variation, and its association with prodromal symptoms. There is some evidence that human herpes virus (HHV) is associated with PR. Drago et al demonstrated HHV-7 as a probable causative agent by detecting HHV-7 in peripheral blood and saliva of patients with PR but not in the control group.5 The association between HHV-7 and PR is controversial, as other studies have failed to replicate similar results. Furthermore, experiments attempting to transmit the disease using isolated HHV-7 have been unsuccessful.
Pityriasis rosea has a characteristic clinical course that makes diagnosis rather straightforward. Traditionally, PR begins with a herald patch: a single, oval-shaped scaly plaque ranging from 2 cm to 5 cm, often on the patient’s trunk. The initial lesion is then followed by the eruption of numerous, smaller lesions, typically within days to a couple weeks. These smaller lesions are salmon-pink, oval to round in shape with a delicate scale, resembling the original herald patch. The generalized rash tends to occur along lines of cleavage of the trunk and neck and is often described as a “Christmas tree” distribution. The lesions may be pruritic, ranging in severity from mild to moderate.6 Constitutional symptoms are usually absent; however, prodromal symptoms of fever, headache, cough, and arthralgia have been found in as many as 59% of patients.7 Most cases resolve in 4 to 6 weeks and rarely last 6 months. Postinflammatory hyperpigmentation is commonly seen in dark-skinned individuals but usually resolves after 6 to 12 months. Recurrence is rare, seen in approximately 2% of patients.5
Atypical clinical presentations of PR can be found in up to 20% of patients. These variations include vesicular, inverse, acral, limb-girdle, and erythema multiforme-like PR. Children often have atypical presentations of PR in both distribution and character of the lesions. The lesions can be folliculo-papular, vesicular, or pustular and can involve the face and distal extremities, sometimes sparing the patient’s trunk.8
The differential diagnosis for pityriasis rosea includes drug eruptions, secondary syphilis, guttate psoriasis, small plaque parapsoriasis, erythema migrans with secondary lesions, erythema multiforme, and tinea corporis. Tinea corporis usually presents with few lesions and can be definitively differentiated by simple KOH scraping. Guttate psoriasis can also present with an acute eruption of small lesions located on the trunk. However, psoriasis has a thicker scale and extended clinical course. Drug eruptions are an important consideration, especially in the context of recent medication changes. Unlike PR, drug eruptions are confluent, brightly erythematous, and more pruritic. Secondary syphilis is an essential diagnosis to consider in atypical presentations of pityriasis rosea. Traditionally, secondary syphilis involves the palms and the soles in the setting of unprotected sexual intercourse and a remote history of a painless chancre. Traditionally, secondary syphilis presents on the palms and soles in patients who report a remote history of a painless chancre.9
Diagnosis of pityriasis rosea is made clinically by history and physical examination revealing the typical clinical presentation of an initial herald patch followed by eruptions of several other pruritic lesions in the absence of other symptoms. Currently, no noninvasive tests are available to confirm the diagnosis of PR. KOH scraping and syphilis serology can easily be obtained and can help rule out other diseases with similar presentations. Skin biopsies are not recommended for diagnosis as PR has nonspecific histopathology that is characteristic but not pathopneumonic. If needed for atypical cases, a skin biopsy would show epidermal focal parakeratosis, a lessened granular layer, spongiosis, spongiotic vesicles, perivascular infiltrate of lymphocytes and histiocytes, and occasionally extravasation of red cells. The characteristic biopsy findings of epidermal dyskeratotic cells and extravasated erythrocytes in the dermis are found in 60% of patients.5
PR is a self-limited disease and spontaneously resolves within 3 months. Therefore, interventions are often not necessary. Treatment includes patient education, reassurance, and symptom management if needed. Medium potency topical corticosteroids can be applied to pruritic areas 2 or 3 times per day for up to 3 weeks if the patient is symptomatic. Topical anti-itch creams containing pramoxine and oral antihistamines may also alleviate pruritus.10 There is limited evidence that oral acyclovir and UVB light may accelerate clinical improvement in severe cases of PR.
The patient and family were reassured. He was given a prescription for fluocinolone oil to use up to twice daily for symptomatic relief, and the rash regressed within several weeks.
Emma Weiss is a medical student at the University of Texas-McCombs School of Business and the Baylor College of Medicine. Jessica Boulavsky, MD, is a dermatology resident at the Baylor College of Medicine in Houston.
- Mahajan K, Relhan V, Relhan A, Garg V. Pityriasis rosea: An update on etiopathogenesis and management of difficult aspects. Indian J Dermatol. 2016;61:375-384. doi:10.4103/0019-5154.185699.
- Chuh A, Chan H, Zawar V. Pityriasis rosea—evidence for and against an infectious aetiology. Epidemiol Infect. 2004;132:381-390. doi:10.1017/S0950268804002304.
- Chuang T-Y, Ilstrup DM, Perry H, Kurland LT. Pityriasis rosea in Rochester, Minnesota, 1969 to 1978. J Am Acad Dermatol. 1982;7:80-89. doi:10.1016/S0190-9622(82)80013-3.
- Chuh AA, Dofitas BL, Comisel GG, et al. Interventions for pityriasis rosea. Cochrane Database Syst Rev. 2007 Apr 18;(2):CD005068.
- Drago F, Broccolo F, Rebora A. Pityriasis rosea: An update with a critical appraisal of its possible herpesviral etiology. J Am Acad Dermatol. 2009;61:303-318. doi:10.1016/j.jaad.2008.07.045.
- Eisman S, Sinclair R. Pityriasis rosea. BMJ. 2015;351:h5233.
- Özyürek GD, Alan S, Çenesizoglu E. Evaluation of clinico-epidemiological and histopathological features of pityriasis rosea. Postepy Dermatol Alergol. 2014;31:216-221. doi:10.5114/pdia.2014.40641.
- Chuh AAT. Quality of life in children with pityriasis rosea: a prospective case control study. Pediatr Dermatol. 2003;20:474-478.
- Marks JG, Miller JJ. Lookingbill and Marks’ Principles of Dermatology. 5th ed. Philadelphia: Saunders; 2013.
- Chuh A, Zawar V, Sciallis G, Kempf W. A position statement on the management of patients with pityriasis rosea. J Eur Acad Dermatology Venereol. 2016;30:1670-1681. doi:10.1111/jdv.13826