Pityriasis Rosea Introduction
Pityriasis Rosea is a common, self-limited, usually asymptomatic, clinically distinctive papulosquamous eruption. More than 75% of patients are between 10 and 35 years of age. Many patients report a mild prodrome or upper respiratory illness within a month of onset.
The onset and clinical course are quite distinctive. The first lesion or herald patch appears, most often on the trunk. The lesion is an oval plaque of 1 to 3 cm in diameter, which develops a thin collarette of residual scale inside the border. 1 to 2 weeks later numerous similar but smaller lesions begin to appear and reach a maximum number within 2 weeks while the herald patch is still present. Lesions usually clear spontaneously in 4 to 12 weeks, without scarring, although postinflammatory pigmentary changes may take months to resolve in darker-skinned people.
Seasonal cases in the spring and fall within the community suggest a viral etiology, though this has not been confirmed. Limited outbreaks have occurred in close quarters such as fraternity houses and military barracks.