eMedicine Specialties > Infectious Diseases > Skin and Soft-Tissue Infections

Pityriasis

Author: Camila K Janniger, MD, Clinical Professor of Dermatology, Clinical Associate Professor of Pediatrics, Chief of Pediatric Dermatology, New Jersey Medical School
Coauthor(s): Rajendra Kapila, MD, MBBS, Professor of Medicine, Department of Medicine, UMDNJ, New Jersey Medical School; Robert L Rogers, MD, Staff Physician, Departments of Internal Medicine and Surgery, Division of Emergency Medicine, University of Maryland; Amal Mattu, MD, FACEP, FAAEM, Program Director, Emergency Medicine Residency, Co-Director, Emergency Medicine/Internal Medicine Combined Residency Program, Department of Surgery, Division of Emergency Medicine, University of Maryland School of Medicine
Contributor Information and Disclosures

Updated: Mar 2, 2009

Introduction

Background

Pityriasis rosea, a rash first described by Gilbert in the 19th century, is a common type of papulosquamous skin eruption that is typically acute in onset and self-limiting. Pityriasis rosea has a distinctive morphology and clinical course and a predilection for young adults. Other types of similar skin eruptions include lichen planus, psoriasis, eczema, and pityriasis rubra pilaris. The rash of pityriasis rosea is scaly in appearance and consists of papules and, sometimes, plaques. The rash is usually short-lived and requires only symptomatic treatment. Pityriasis rosea evolves rapidly and usually begins with the well-known herald patch.

Frequency

United States

Pityriasis rosea is very common in the general population, and most cases occur in the spring and winter in temperate climates. The estimated frequency of pityriasis rosea in the United States is approximately 0.13% in females and 0.14% in males.

International

Pityriasis rosea is more common in certain countries (eg, Uganda).

Mortality/Morbidity

Pityriasis is a self-limiting illness that causes very little morbidity. It follows a benign course in most patients, and complete resolution of symptoms is the rule. However, some cases of severe eczematous or drug-induced rashes may be protracted. These cases are known as pityriasis rosea perstans.

Race

Pityriasis has no predilection for any race.

Sex

The incidence of rash development is slightly higher in females than in males.

Age

Approximately 87-90% of pityriasis cases occur in people aged 10-40 years. Pityriasis is rare among very young and very old persons.

Clinical

History

• Patients with pityriasis may report a history of nonspecific symptoms (eg, malaise, nausea, fever) that precede the development of the rash.
• Obtain a detailed dermatologic history in all patients.
  • Ask patients about prior dermatologic diseases and their manifestations.
  • Elicit symptoms of the presenting rash (eg, pruritus, pain).
• When pertinent, obtain a history of sexually transmitted diseases.
• Record travel history, occupational exposure, and drug exposure in the medical record.
• Ask patients about ill contacts.
• The natural history of pityriasis rosea in black children may differ from that described in American, European, and African literature. A study by Amer et al (2007) found that black children with pityriasis rosea had more frequent facial (30%) and scalp lesions (8%) involvement than anticipated in white populations. One third had the papular form of pityriasis rosea.¹

Physical

• The initial skin lesion of pityriasis is a pink (rosea) oval patch approximately 3-6 cm in diameter that can develop anywhere on the body, including on plantar skin, although it is most commonly located on the back.² This is referred to as the herald patch.
  • The herald patch has a scale (pityriasis) that resembles a collarette toward the periphery.
  • The patch is something of a dermatologic enigma because it does not occur in any other known skin disease. The earliest stages of the patch may manifest as pink papules that can be mistaken for other lesions (eg, insect bites).
• A few days later, the initial patch is followed by a rash of similar but smaller lesions.
  • Secondary eruptions appear in crops at intervals of a few days and reach a maximum in about 10 days.
  • The rash typically follows the cleavage lines of the skin, resulting in a Christmas tree–type pattern.
  • The secondary rash is generally distributed on the back, chest, abdomen, arms, and thighs.
  • The rash can last up to 6-8 weeks before fading.
• Lesions are typically symmetric and are not preceded by systemic symptoms.
• Pruritus appears to be the predominant symptom but can be absent in as many as 25% of cases.
• Individuals with dark skin can have a postinflammatory hyperpigmentation that may take a few months to heal. Both hypopigmentation and hyperpigmentation can follow the rash.
• The following atypical features occasionally occur:
  • Herald patch is absent in 10-50% of cases.
  • Skin eruptions may be florid.
  • Lesions may be few, large, and in a particular body region (eg, axilla). In adults, this is known as pityriasis circinata et marginata of Vidal.
  • Rash may be located in areas not usually affected by pityriasis; this is known as inverse pityriasis rosea.
  • Pityriasis may occur in sun-spared areas such as the breast and the axilla.
  • Lesions are sometimes papular, vesicular, or purpuric.

Causes

• An infectious etiology for pityriasis rosea has been sought for many years.
• A viral agent was once postulated as a precipitant for pityriasis rosea. Over the past few years, there has been considerable interest in human herpesvirus 7 as a possible etiologic agent. Investigative studies have failed to link this virus, as well as others, to the well-known rash of pityriasis rosea.³
• Some investigators believe that a fungal infection is more likely.
• Thus far, the search for an infectious agent has been unsuccessful.
• The incidence of pityriasis rosea among dermatologists is 3-4 times that of other physicians.
• Recurrences of pityriasis rosea are generally regarded as rare and are thought by some to indicate a lasting immunity when they do occur.
• Certain medications have been implicated as possible causes of pityriasis rosea.⁴ Adalimumab was recently linked with pityriasis rosea.⁵

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