[Genetic studies on the ossification of the posterior longitudinal ligament]

The genetic mechanism of OPLL (ossification of the posterior longitudinal ligament) was investigated through a family study including 62 probands and 129 relatives using X-ray examination of the spine. The study showed that the prevalence of OPLL was 29.1% in men and 25.7% in women with a tendency of increase with age. As the mode of inheritance, the segregation ratio or children of probands was that of simple recessive; the segregation ratio of siblings was either simple recessive or dominant. The recurrence rate of siblings excluded polygenes; this mode of transmission and the penetrance suggested that the most probable mode of inheritance of OPLL would be simple dominant. As genetic markers, various blood groups, serum groups, and erythrocyte isozyme groups were examined in 23 patients with OPLL. Gc serum groups and EsD isozyme groups displayed some association with OPLL in comparison with the normal controls.