SEX-RATIO IN THE SPONDYLOARTHROPATHIES AND ITS RELATIONSHIP TO PHENOTYPIC-EXPRESSION, MODE OF INHERITANCE AND AGE AT ONSET

Objective. To investigate the interrelated effect of phenotypic expres sion [i.e., primary ankylosing spondylitis (1 degrees AS) or disease s econdary to psoriasis (Ps)AS or inflammatory bowel disease (IBD)AS], a ge at onset, sex and inheritance of responsible genes in AS. Methods. Three studies were performed to evaluate 1949 subjects with AS. Subgro ups of the patients were formed for each study depending on disease ty pe (1 degrees AS = 1695; Ps AS = 173; IBD AS = 81), nature of inherita nce or age at onset of AS symptoms. These groups were further subdivid ed to assess the effect of sex. Results. The sex ratio of the entire g roup was 2.6:1 in favor of men. However, IBD AS had an equal sex distr ibution as does IBD alone. By contrast, Ps, which has an equal sex rat io as a lone event or in association with arthritis, resulted in a mal e dominance of 4.1:1 when it occurred as Ps AS. Women with IBD AS had a significantly younger onset compared to women with 1 degrees AS [mea n onset 21.7 years (SD 6.65) vs mean onset 24.4 years (SD 9.79), respe ctively; p = 0.019]. A younger age at onset was found in women with fa milial disease [mean 22.2 years (SD 7.55)) compared with the mean onse t of sporadic disease in women [24.5 years (SD 10.0); p = 0.0059]). Th ere was a progressive fall in the sex ratio as the age at onset increa sed (p = 0.053). For example: M:F ratio of < 20 years old was 3:1 comp ared to 1.8:1 for those with an onset of > 40 years. Conclusion. Sex r atio and age at onset are influenced both by each other and such facto rs as disease type and familial versus sporadic occurrence. These data help provide a predictable pattern of disease in spondyloarthropathy.