{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,27]],"date-time":"2026-09-27T08:06:41Z","timestamp":1790496401610,"version":"4.1.0"},"reference-count":44,"publisher":"Wiley","issue":"8","license":[{"start":{"date-parts":[[2007,7,30]],"date-time":"2007-07-30T00:00:00Z","timestamp":1185753600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Arthritis &amp; Rheumatism"],"published-print":{"date-parts":[[2007,8]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Objective<\/jats:title><jats:p>Patients with ankylosing spondylitis (AS) and \u223c50% of their first\u2010degree relatives may have a genetic abnormality that results in subclinical intestinal inflammation. This study was undertaken to examine the familial occurrence and cosegregation of AS and inflammatory bowel disease (IBD) in order to determine whether there is a shared genetic risk factor in families.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>The Icelandic genealogy database and population\u2010wide data on all living Icelanders diagnosed as having AS (n = 205) and\/or IBD (n = 1,352) were used to estimate the risk ratios of AS for relatives of patients with AS, the risk ratios of IBD for relatives of patients with IBD, and the cross\u2010risk ratios of AS for relatives of patients with IBD or of IBD for relatives of patients with AS. The mean kinship coefficients for each disease were calculated. The control population for disease risk calculations comprised 10,000\u2013100,000 sets of matched Icelandic subjects.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>First\u2010, second\u2010, and third\u2010degree relatives of patients with AS had risk ratios of 94, 25, and 3.5, respectively, indicating an increased risk of developing AS (each <jats:italic>P<\/jats:italic> &lt; 0.0005), while first\u2010, second\u2010, and third\u2010degree relatives of patients with IBD had risk ratios for IBD of 4.4, 2.2, and 1.4, respectively (each <jats:italic>P<\/jats:italic> &lt; 0.0001). The cross\u2010risk ratios of IBD were 3.0 and 2.1 in first\u2010 and second\u2010degree relatives of patients with AS, respectively, and were the same for AS in first\u2010 and second\u2010degree relatives of patients with IBD. With the exception of Crohn's disease, the risk of having AS, ulcerative colitis, or IBD in spouses of patients with these diseases did not differ significantly from that in controls. Calculation of the kinship coefficients confirmed these patterns of familial risk.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>Patients with AS or IBD in Iceland are significantly more related to each other than are randomly sampled control subjects, in terms of an increased risk of either or both conditions developing in third\u2010degree relatives. These findings suggest that one or more undiscovered genetic variants may underlie the risk of both diseases.<\/jats:p><\/jats:sec>","DOI":"10.1002\/art.22812","type":"journal-article","created":{"date-parts":[[2007,7,30]],"date-time":"2007-07-30T16:18:27Z","timestamp":1185812307000},"page":"2633-2639","source":"Crossref","is-referenced-by-count":81,"title":["A common genetic background for inflammatory bowel disease and ankylosing spondylitis: A genealogic study in Iceland"],"prefix":"10.1002","volume":"56","author":[{"given":"Bjarni","family":"Thjodleifsson","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"\u00e1rni J.","family":"Geirsson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sigurdur","family":"Bj\u00f6rnsson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ingvar","family":"Bjarnason","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2007,7,30]]},"reference":[{"key":"e_1_2_7_2_2","doi-asserted-by":"publisher","DOI":"10.1093\/rheumatology\/XXVII.suppl_2.110"},{"key":"e_1_2_7_3_2","doi-asserted-by":"publisher","DOI":"10.1136\/gut.42.3.387"},{"key":"e_1_2_7_4_2","doi-asserted-by":"publisher","DOI":"10.1177\/003591576605900532"},{"key":"e_1_2_7_5_2","first-page":"2295","article-title":"Ankylosing spondylitis: at the interface of bone and cartilage","volume":"27","author":"Maksymowych WP","year":"2000","journal-title":"J Rheumatol"},{"key":"e_1_2_7_6_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0016-5085(03)00385-8"},{"key":"e_1_2_7_7_2","doi-asserted-by":"publisher","DOI":"10.1080\/003655200451207"},{"key":"e_1_2_7_8_2","doi-asserted-by":"publisher","DOI":"10.1053\/gast.1996.v111.pm8780562"},{"key":"e_1_2_7_9_2","doi-asserted-by":"publisher","DOI":"10.1053\/gast.1996.v111.pm8780561"},{"key":"e_1_2_7_10_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.1135245"},{"key":"e_1_2_7_11_2","doi-asserted-by":"publisher","DOI":"10.1038\/35079107"},{"key":"e_1_2_7_12_2","doi-asserted-by":"publisher","DOI":"10.1038\/35079114"},{"key":"e_1_2_7_13_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0016-5085(03)00383-4"},{"key":"e_1_2_7_14_2","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1016\/S0889-857X(21)00706-7","article-title":"Gut and spondyloarthropathies","volume":"18","author":"Leirisalo\u2010Repo M","year":"1992","journal-title":"Rheum Dis Clin North Am"},{"key":"e_1_2_7_15_2","doi-asserted-by":"publisher","DOI":"10.1093\/rheumatology\/27.2.163-b"},{"key":"e_1_2_7_16_2","first-page":"499","article-title":"Subclinical involvement of the gut in undifferentiated spondylarthropathies","volume":"7","author":"Mielants H","year":"1989","journal-title":"Clin Exp Rheumatol"},{"key":"e_1_2_7_17_2","first-page":"2266","article-title":"The evolution of spondyloarthropathies in relation to gut histology. 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