1.5.5 Pityriasis Rosea

It affects adolescents and young adults (aged 10 to 35 years). Incidence is 0.68/100 dermatology patients, prevalence 0.5-2% with a peak incidence in spring and autumn.

Acute, disseminated, self-limiting symmetrical papulo-squamous exanthem with typical collarette scale.

The disease was first described by Gibert in 1860. The etiology of PR remains largely uncertain, with hypotheses directed towards either infectious HHV and others or non-infectious origins (post vaccination) or both. It probably arises as an “id”- reaction to some viral infections (human herpes virus 6 in adolescence or 7 in adults (HHV6/7). Thereafter long-life immunity exists. In HIV immunocompromised patients it can be seen more often and was reported during the corona epidemic quite more often, but more a pattern which was pityriasis rosea-like. There is also evidence that dermatologists are more often affected than other members of medical disciplines.

The initial lesion is a large erythematous (salmon coloured) patch (herald patch, medallion, tâche- mère), up to 5 cm in diameter), followed by multiple smaller lesions frequently following skin lines (e.g. Christmas tree distribution around ribs) being thin with a typical collarette scale. Similar long axis orientation for individual patches.

Pruritus can occur (50%) and is variable in intensity, especially when skin is irritated (intense washing, drying medications or with simultaneous concurrent dermatitis). In children sometimes a so-called inverse form can occur and manifests in the axillae and the groin region.

Post-inflammatory hypopigmentation or hyperpigmentation (lighter or darker patches of skin) can occur.

Prodromal symptoms (fever, headache, arthralgia, cough, vomiting, or lymphadenopathy) have been reported in 60% of the patients.

Common disease. Up to 20% atypical clinical variants can occur, more often in children.

Not required, but syphilis should be ruled in adults.

Primarily not required. In case of unusual course or atypical pattern. No specific pattern with edema in the stratum papillary, mild epidermal spongiosis and some spotted parakeratosis.

Different relapse rates are reported (1-3% up to 26% in 4 years).

No evidence of any preventive measurements or effective treatment.

Mild skin care and avoidance of irritating factors. If pruritic, topical anti-pruritic agents: mild corticosteroids or emollients. In selected cases UVB 311nm.

Statins and antihistaminics, which induce a sebostatic effect, may enhance the disease severity.