Pityriasis rosea--an update.

Recent controversies on the etiology, diagnosis and treatment have led to increased interest in pityriasis rosea (PR). We review these aspects of the disease. PR is universal. The incidence is around 0.68 per 100 dermatological patients, or 172.2 per 100,000 person-years. The prevalence in people aged between 10 and 29 years is 0.6%. The male to female ratio is around 1:1.43. Evidence on seasonal variation is conflicting, but there is no evidence that the incidence is dependent on mean air temperature, mean total rainfall, or mean relative humidity. Spatial-temporal and temporal clustering of cases of PR has been reported. The association of PR with human herpesvirus-7 infection is still controversial. Owing to the extreme high sensitivities of sequence-based detection methods such as polymerase chain reaction, novel criteria should be applied to evaluate the evidence. There is no evidence that PR is associated with other viral or bacterial infections. The role of autoimmunity in PR warrants further investigations. Many patients with PR have one or more atypical features. Application of validated diagnostic criteria may be helpful for atypical cases. The efficacy of macrolides, including erythromycin, in PR is still under evaluation. There is no evidence that antiviral agents are effective. The efficacies of ultraviolet radiotherapy and systemic corticosteroids are not well established. In managing a patient with PR, we should concentrate more on how the eruption is affecting the quality of life, i.e. the illness, rather than the extent and severity of the eruption, i.e. the disease.