Pityriasis rosea is a chronic keratotic inflammatory skin disease that occurs in children aged 1 to 10 years and adults aged 40 to 50 years, independent of the season, and presents as orange-red patches, layered nails, hyperkeratosis under the nails, puckering of the surface and may present as diffuse hair loss.
In contrast, pityriasis rosea mostly occurs in young or middle-aged adults, with a high prevalence in spring and autumn, the initial damage is a rose-coloured light red patch of 1-3cm in diameter size with fine scales on the trunk or extremities, called a prodromal patch, the number is 1 to 3, after 1 to 2 weeks red patches of varying sizes appear on the trunk and extremities, often symmetrically distributed, and can be differentiated by pathological examination.