Family studies in Bechterew's syndrome (ankylosing spondylitis) III. Genetics

The results of segregation analyses in 75 families where the proband had ankylosing spondylitis, are presented. Of the 278 adult, living first degree relatives, approximately 85% cooperated in the study. Clinical and radiographical examinations were performed and HLA typing was conducted. The results were in agreement with our hypothesis that ankylosing spondylitis is part of a syndrome where different genetic factors interact. Such known factors are HLA B27 associated disease susceptibility, susceptibility to psoriatic arthropathy and susceptibility to entero-arthropathy. Radiographical sacro-iliitis was restricted to HLA B27 positive relatives, and was more frequently found in relatives to probands with psoriasis than in relatives to probands without psoriasis. Environmental factors (intestinal bacteria) are known to trigger the disease at least in some persons, and we have postulated that all or most of them have the predisposition to develop disease. Thus, the syndrome has a multifactorial etiology. The phenotypic expressions of the different genetic predispositions involved, include sacro-iliitis, psoriasis, acute anterior uveitis, peripheral arthropathy and inflammatory bowel disease. We suggest the descriptive name HEREDITARY MULTIFOCAL RELAPSING INFLAMMATION (HEMRI) for this syndrome. Ankylosing spondylitis, psoriatic arthropathy and entero-arthropathy may be regarded as clinical sub-types of the syndrome.