Pityriasis

OBJECTIVES

After completing this article, readers should be able to:

1. Describe who is affected most commonly by pityriasis rosea and for how long.

2. Delineate the characteristics of the classic form of pityriasis rosea.

3. Describe the etiology of pityriasis rosea.

4. List the drugs and vaccines that can cause an eruption that mimics pityriasis rosea.

5. List the differential diagnosis of pityriasis rosea, especially among patients whose palms and soles are involved.

6. Describe appropriate treatment for pityriasis rosea.

Introduction

Pityriasis rosea (PR) is an acute, self-limited inflammatory disorder that most commonly affects otherwise healthy children and adolescents. First called pityriasis rosea by the eminent French physician, Camille Gilbert, in 1860, the condition has been described in the literature for almost 200 years. The name is derived from Greek (pityriasis = scaly) and Latin (rosea = pink). Traditionally it is listed in textbooks as a papulosquamous condition. Although it is easily recognizable in its typical presentation, atypical forms may pose a diagnostic challenge. Secondary syphilis always must be considered in the differential diagnosis.

Epidemiology

PR is seen throughout the world in all seasons. There is no marked seasonal predisposition, but some studies suggest an increase in spring and fall. PR affects all ages, but approximately 50% of cases occur before the age of 20 years; the incidence is greatest among adolescents. Only 4% of cases occur before age 4, and it is rare before age 2. There is a slight female predominence. Support for an infectious etiology comes from observed clustering of cases and reports of scattered “epidemics.”

Pathogenesis

There is a widely held belief that PR is a viral infection. Many observations support this view, including the clustering …