Abstract
Genetic factors have been implicated in osteoarthritis (OA), particularly in OA of the hip joint (hip OA). Several instances of familial hip OA that show distinctive modes of inheritance but that differ from chondrodysplasia have been reported. Here, we report the characterization of a large Japanese family with an inherited disease of the hip that is indistinguishable from common hip OA, as evidenced by clinical symptoms and radiographs of the joint. This family contained eight patients in 4 generations. Affected individuals develop pain in the hip joint during adolescence, and the disease progresses to severe crippling before age 60 years. Patients generally are in good health, height is not reduced, and there is no extraskeletal involvement suggestive of chondrodysplasia. The skeletal change is bilateral acetabular dysplasia followed by OA, which occurs after age approximately 40 years and is indistinguishable from idiopathic nonfamilial dysplastic hip OA. This trait shows autosomal dominant inheritance, with a considerably consistent phenotype. Genomewide screening revealed linkage at chromosome 13q22, and haplotype analysis narrowed the locus to a 6.0-cM interval between markers D13S1296 and D13S162, with a maximal multipoint LOD score of 3.57. The family described here represents a novel genetic entity as a monogenic form of hip OA. Its further characterization can aid in elucidating the etiology and pathogenesis of a common idiopathic form of OA.