Low prevalence of psoriasis among children and adolescents in a large multiethnic cohort in southern California

BackgroundLittle information is available on the prevalence of psoriasis in children and adolescents.ObjectiveWe sought to estimate the prevalence of pediatric psoriasis in southern California and to investigate the validity of psoriasis diagnosis by a dermatologist compared with a nondermatologist.MethodsIn a southern California population of 710,949 children who were enrolled in an integrated prepaid health plan in 2007 through 2008, cases of psoriasis were identified from electronic medical records and validated by medical chart review. Positive predictive values for valid diagnosis were reported for dermatologists and nondermatologists.ResultsThe prevalence of pediatric psoriasis confirmed by medical chart review was 19/10,000 patients. The prevalence of psoriasis diagnosis (confirmed and unconfirmed) was 30/10,000 patients. The age at onset of psoriasis was slightly earlier in boys than in girls. The positive predictive value for a valid diagnosis of psoriasis was 63.7% when the diagnosis was made by any health care provider, 90.0% by a dermatologist, and 26.6% by a nondermatologist. The prevalence of psoriasis was higher in girls than in boys. Psoriasis affected 29 (95% confidence interval [CI] 27-32) non-Hispanic whites, 20 (95% CI 16-24) Asian/Pacific Islanders, 16 (95% CI 15-18) Hispanic whites, and 6 (95% CI 4-9) blacks per 10,000 patients.LimitationsInformation on the age at onset was estimated based on the first documented diagnosis of psoriasis.ConclusionThe overall prevalence of pediatric psoriasis was lower compared with other published studies. This could be in part a result of underdiagnosis because of greater sunlight exposure in southern California and a lower proportion of non-Hispanic whites in the population.