Prevalence of psoriasis in a Norwegian Lapp population.

The occurrence of psoriasis in a Norwegian Lapp population was estimated by reviewing medical records in the local health centre of Kautokeino. Altogether 40 cases of psoriasis were registered in the study population comprising 99.6% of the total population of 2,963 individuals. Thirty-five cases of psoriasis belonged to the Lappish population of 2,508 people, giving a prevalence of 1.4%, with no difference between males and females. Five cases of psoriasis were found in the non-Lappish population of 442 individuals which gives a prevalence of 1.1% with no sex differences. A peak prevalence among Lapps was observed in the age groups 20-39 years (2.7%), equal for both sexes and in females aged 50-59 years (3.2%), whereas a lower prevalence of 0.6% was found in the age group 40-49 years. A seronegative psoriatic arthritis was recorded in 6 of the 35 Lappish compared to none of the non-Lappish cases. A familial association was confirmed in 11 of the 35 Lappish cases, in none of the non-Lappish.