Pityriasis Rosea

Essentials

• Pityriasis rosea is a self-limiting exanthematous disease.
• Diagnosis is based on clinical presentation and the two-phase course of the disease.
• Treatment is symptomatic.

Aetiology

• In many cases caused by HHV6/HHV7 viral infection or reactivation
• Triggering factors may include some other viral infections, drugs or vaccinations.

Course of the disease

• The typical two-phase course is diagnostic.
• A solitary initial patch “heralds" the eruption (picture ), often on the trunk or the chest.
  • A well-demarcated, erythematous, oval lesion which later on develops a collarette of fine scale inside the border (pictures )
  • Occasionally the herald patch is absent.
• A few weeks after the herald patch, several smaller (0.5-3 cm in diameter), oval-shaped, salmon-pink patches, the longitudinal axis of which mainly follow the tension lines (e.g. rib-lines), appear in a pox-like fashion on the trunk and proximal extremities (pictures ).
• Mild pruritus is sometimes present. The skin lesions can be irritated by external factors (e.g. washing, sauna etc.)
• The condition is not contagious, and it may occur more frequently in spring and autumn.

Differential diagnosis

• Drug eruptions (picture ) may resemble widespread pityriasis rosea.
• Guttate psoriasis Psoriasis is often associated with genetic predisposition, and scaling is generally more prominent (picture ). It is often triggered by streptococcal tonsillitis.
• Tinea versicolor (pictures ) is lighter coloured and develops more slowly. The patches are usually not reddish and the rash is not preceded by a herald patch.
• Tinea corporis may mimic the herald patch (picture ); in some cases fungal samples are indicated (for microscopy and culture).
• Secondary syphilis (picture ) Syphilis is rare in industrialised countries. When clinically suspected, it can be excluded with an antibody assay (serum Treponema pallidum antibodies)

Treatment

• In most cases, all that is needed is reassurance that the prognosis is good and the lesions are benign.
• Usually resolves spontaneously within 6-8 weeks, but may persist longer. Recurrence is not common.
• If required, pruritus may be alleviated with moderately potent to potent topical glucocorticoids or oral antihistamines.
• The avoidance of exposure to irritant agents (e.g. sauna) may be beneficial.
• In severe or prolonged cases aciclovir 400 mg 3 times daily Interventions for Pityriasis Rosea for a period of one week.

Specialist consultation

• Prolonged disease may often require the intervention of a dermatologist. UVB light treatment, for example, may be used to manage the condition.

Pictures