Incidence and genetic aspects of patellar luxation in Pomeranian dogs in Thailand

There is a high incidence of patellar luxation (PL) in Pomeranian dogs from Thailand. DNA samples were collected from 59 dogs originating from 15 families. PL was present in 75% of the dogs with a male:female ratio of 1:1.95. Polymorphic microsatellites situated close to the COL6A1, COL6A3, COL9A1, COL9A2, and COL9A3 genes were analyzed for linkage to the phenotype. Sibling-pair analysis revealed that none of the collagen markers analyzed had a high non-parametric linkage score with the highest score, 1.56, for COL9A2 (P = 0.07). The low LOD scores for these collagen genes indicated a non-involvement in the pathogenesis of PL in Pomeranians. An association study with a low density single nucleotide polymorphism (SNP) set indicated the possible involvement of a region on chromosome 7. The association of this region remained indicative when larger groups of 43 cases and 40 controls were compared (Chi square test P = 0.01).