Pityriasis rosea

Pityriasis rosea (PR) Gibert is an eruptive benign acute disorder manifested by erythematous-squamous lesions which are self-resolving. In most cases it affects subjects between the ages of 10 and 35. The incidence is low in the first stages of life: only 14% of cases under the age of 10, rare in the first 2 years of life and exceptional in the first months.

Aetiology

Its course, the seasonal onset sometimes in clusters and the rarity of recurrences suggest a viral origin. Individual predisposition has also been suggested. Rarely preceded by prodromes such as ill-being, headache and nausea, in most cases the dermatosis arises with an isolated patch, also called herald patch or medallion, roundish or oval in shape, with a diameter of 2-3 cm and yellowish-pink in colour, with an initially wrinkly “cigarette paper” surface. When fully developed, it forms an annular shape with a thin squamous edge between the pinkish peripheral area and the yellowish central area. Its predominant locations are the trunk, arms, neck and thighs. Usually there are no subjective symptoms. After 1-3 weeks the secondary eruption appears, characterised by erythematous-squamous lesions with the morphological characteristics of the herald patch but smaller, and/or lenticular lesions covered with pityriasis plaques. These symptoms can coexist; sometimes papular or vesicular lesions may be observed. The lesions are typically distributed in a regular pattern, in a variable number, along “Christmas tree” cleavage lines, forming a fir tree shape. The face and distal end of the limbs are usually spared.

The mucous membranes may be affected, especially the oral cavity, with various manifestations such as red maculae, petechiae, vesicles or erosions. This location is more common in children. The nails may also be affected, with dystrophic changes. Pruritus is present in about 75% of cases, especially in children. It follows a course of spontaneous resolution without sequelae after 6-8 weeks, and recurrences are rare. In about 20% of cases, PR presents in atypical form with regard to morphology, distribution of lesions or course. A new classification of the atypical cases has recently been proposed. PR with atypical morphology of lesions includes the vesicular form, sometimes very extensive and associated with intense pruritus and more common in children and young adults; the purpuric form and the urticarial form. PR atypical because of size of lesions includes PR gigantea of Darier and the papular form with small components, 1-2 mm in diameter, more common in children. The form atypical because of distribution of the lesions includes inverse PR, which affects the face, armpits and inguinal folds and the unilateral asymmetric forms. Regarding the number of lesions, there are forms of PR with lesions that are large and few in number (PR circinata et marginata) and localised forms. In PR with atypical locations, the symptoms affect the face, head, hands and feet. In some forms the pruritus is severe, sometimes accompanied by pain or burning. The complications include eczematisation due to easy irritability of the lesions. If only the initial patch is present, differential diagnosis is mainly with mycosis, eczema in patches and eczematide. Secondary lesions should be differentiated from eczematide, pityriasis lichenoides, psoriasis and rosea-like drug-induced eruptions.

Browse for more pediatric pathologies