Recent progress in the study of pathogenesis of ossification of the posterior longitudinal ligament.

The pathogenesis of ossification of the posterior longitudinal ligament (OPLL) is still unknown. Gene analysis and molecular biology have been introduced in recent years, and etiologic and pathological clarifications are being achieved. An important role of the genetic background in the development of this disease was demonstrated by pedigree survey, twin survey, and HLA haplotype study. The results of gene linkage study showed that patients with OPLL have a significantly higher incidence of genetic abnormalities found in the XI collagen (alpha)2 gene (COL11A2) region. From the gene mapping of this abnormality, the abnormal N-propeptide of the COL11A2 gene was found to be responsible. We are planning to undertake genetic analysis of the whole of chromosome VI to find the pathogenic genes responsible for OPLL in addition to COL11A2. A cell biological approach is also necessary to make clear the relationship between abnormalities of the COL11A2 gene and ossification of the ligament. In future, identification of the susceptible gene, elucidation of its function, and study toward the development of preventive and therapeutic drugs will advance.