Incidence of psoriasis in children: A population-based study

Background: Although psoriasis is considered to have a dual peak in age of onset, currently no studies exist regarding the incidence of psoriasis in children. Objective: The objective of this study was to determine the incidence of psoriasis in childhood. Methods: A population-based incidence cohort of patients aged younger than 18 years first given the diagnosis of psoriasis between January 1, 1970, and December 31, 1999, was assembled. The complete medical record of each child was reviewed and psoriasis diagnosis was validated by a confirmatory diagnosis in the medical record by a dermatologist or medical record review by a dermatologist. Age- and sex-specific incidence rates were calculated and were age and sex adjusted to 2000 US white population. Results: The overall age- and sex-adjusted annual incidence of pediatric psoriasis was 40.8 per 100,000 (95% confidence interval: 36.6-45.1). When psoriasis diagnosis was restricted to dermatologist-confirmed subjects in the medical record, the incidence was 33.2 per 100,000 (95% confidence interval: 29.3-37.0). Incidence of psoriasis in children increased significantly over time from 29.6 per 100,000 in 1970 through 1974 to 62.7 per 100,000 in 1995 through 1999 (P < .001). Chronic plaque psoriasis was the most common type (73.7%), and the most commonly involved sites were the extremities (59.9%) and the scalp (46.8%). Limitations: The population studied was a mostly white population in the upper Midwest. Conclusion: The incidence of pediatric psoriasis increases with increasing age. There is no apparent dual peak in incidence. The incidence of pediatric psoriasis increased in recent years in both boys and girls.