The extent of ossification of posterior longitudinal ligament of the spine associated with nucleotide pyrophosphatase gene and leptin receptor gene polymorphisms.

Study Design: A case-control study using radiograph findings and the PCR assay with regard to the susceptibility and the severity of ossification of posterior longitudinal ligament of the spine (OPLL).

Objective: To analyze whether polymorphisms of the nucleotide pyrophosphatase (NPPS) gene and the leptin receptor gene predispose to an increased frequency and severity of OPLL.

Summary Of Background Data: The NPPS gene is responsible for ectopic ossification in the ttw mouse, an animal model for OPLL. The Zucker fatty rat, another animal model for OPLL, has a missense mutation in the leptin receptor gene.

Methods: Analysis of 172 OPLL patients and 93 non-OPLL controls was performed. Radiographs of the cervical, thoracic and lumber spine were analyzed to determine whether OPLL was present and to what degree. Genomic DNA was extracted from all participants. Polymorphisms of the NPPS gene and the leptin receptor gene were analyzed using the PCR assay. The association of the polymorphisms with the development and extent of OPLL were statistically evaluated.

Results: No significant association was found between the polymorphisms and the existence of OPLL in both the NPPS and the leptin receptor genes. However, the IVS20-11delT variant in the NPPS gene and the A861G variant in the leptin receptor gene were more frequent in patients with OPLL in the thoracic spine compared with patients whose OPLL was restricted to the cervical spine.

Conclusion: The present results suggest that the IVS20-11delT variant of the NPPS gene and the A861G variant of the leptin receptor gene are associated with more extensive OPLL, but not with the frequency with which it occurs.