To examine the genotypic and phenotypic characteristics of a Micronesian kindred with autosomal dominant precocious osteoarthritis (OA).
We reviewed records and radiographs of 3 index patients and their parents, administered questionnaires to 16 additional kindred members, performed whole-genome scans of 24 family members, and sequenced relevant genes from 16 family members.
The kindred displayed early onset OA, enlarged epiphyses, platyspondyly, and brachydactyly with dysplastic findings consistent with mild spondyloepiphyseal dysplasia. Genetic analysis revealed an arginine to cysteine substitution at position 75 of the collagen 2A1 gene, a mutation that has been described in 4 other geographically distinct families. The major phenotypic differences among the families were in height (ranging from short to tall) and hearing loss noted in 3 of the 5 families.
The presence of the COL2A1 Arg75Cys mutation in 5 geographically distinct areas helps to confirm a potential mutational hotspot. The diverse phenotypic spectrum suggests that modifier genes and environmental factors play a role in the expression of this mutation.