The familial form of spondylarthropathy - A clinical study of 115 multiplex families

Objective. To investigate the interrelationships among different phenotypes , and their relationship to theHLA-Blocus,inmultiplexfamilieswithspondylart hropathy (SpA). Methods. We recruited 115 white French families, each of which had at least 2 members with SpA. Pedigrees were established. Clinical data and pelvic r adiographs were collected, The HLA-B27 status of all patients was determine d. Analysis was performed to determine the prevalence of SpA. manifestation s according to sea, disease duration, and HLA-B status, and to examine clus tering of specific manifestations in subsets of families. Results. We identified 329 SpA patients. Mean +/- SD age at onset was 24 +/ - 9.4 years. The male:female ratio nas 186:143, or 1.3, with few sex differ ences in disease expression. Axial manifestations and HLA-B27 were each pre sent in 97% of the patients, Inflammatory bowel disease and HLA-B35 were ov errepresented in the 7 families containing HLA-B27-negative patients. The f requency of radiographic sacroiliitis increased in parallel with disease du ration. Peripheral enthesitis, radiographic sacroiliitis, and psoriasis wer e evenly distributed in the families. Clustering independent of age was onl y observed for peripheral arthritis, suggesting that specific factors may p redispose individuals to this manifestation. Conclusion. Familial SpA appears to be homogeneous, based on the high frequ encies of axial skeletal involvement and HLA-B27. The lack of clustering of most manifestations in families suggests that a predominant shared compone nt, including HLA-B27, predisposes individuals to all forms of familial SpA , and that ubiquitous genetic or environmental factors contribute to phenot ype diversity.