Actinic prurigo: Clinical features and HLA associations in a Canadian Inuit population

Background: Actinic prurigo (AP) is an idiopathic familial photodermatitis. AP of the Inuit is rarely reported and poorly characterized. Objective: Our purpose was to examine the clinical features and HLA associa tions of AP in an Inuit population. Methods: Thirty-seven Inuit subjects with AP were administered a questionna ire and underwent a cutaneous examination. Other causes of photosensitivity were excluded. HLA class I typing was performed by polymerase chain reacti on and sequence-specific primers and class II typing by polymerase chain re action and sequence-specific oligonucleotide probes. Results: Subjects were 81.1% female, 67.6% had a family history of photosen sitivity, and all experienced seasonal variation. The average age at onset of photosensitivity was 29 years, and only 27% had a trend toward improveme nt in photosensitivity. Involvement of eyes and nonexposed skin was reporte d in 62.2% and 18.9% of subjects, respectively. Physical examination reveal ed involvement of the face (64.9%), lip (32.4%), ear (13.5%), and dorsal as pect of the hand (24.3%). HLA-DRB1*14 was present in 51.2% of subjects and 26.2% of controls (P = .022, odds ratio = 2.975). This is a previously unre ported HLA association. Conclusion: AP in the Inuit is a seasonal, pruritic photodermatitis, often commencing in adulthood and worsening over time. A novel association with H LA-DRB1*14 has been discovered. Overall, this novel HLA association, the ab sence of HLA associations previously reported in non-Inuit. populations, an d clinical distinguishing features support the concept that AP in the Inuit may have a distinct immunopathogenic basis that translates into a differen t phenotype. It also raises the question of whether AP in the Inuit is a di stinct photosensitivity disorder specific to this group that has been genet ically isolated because of geographic and cultural seclusion.