Susceptibility loci for atopic dermatitis on chromosome 21 in a Swedish population

Background: Atopic dermatitis (AD) is a hereditary, pruritic, chronic, relapsing, inflammatory skin disease resulting from multiplex interactions between genes and environmental factors. We have previously found several loci showing suggestive linkage on chromosomes 3q14, 13q14, 15q14-15 and 17q21, and weaker linkage to chromosomes 1p32, 4q24-26 and 21q21 in 109 Swedish families. Methods: In order to confirm the linkage to chromosome 21, we carried out a replication linkage analysis with additional microsatellite markers on chromosome 21 in another set of 295 families. Results: In the extended material, the Z-score was 2.40 (P < 7.4 x 10(-4)) in the region 21q21 for a semi-quantitative variable measurement; the severity of AD. When combining the two data sets into 404 families and stratifying according to asthma status, suggestive linkage was found only in the group of AD patients who also had asthma (Z-score 2.45, P < 7.4 x 10(-4) and 2.69, P < 7.4 x 10(-4)) in two different regions. Conclusions: Our results suggest that 21q21 could contain a susceptibility gene modulating the severity of AD especially in combination with asthma.