TGFBR2 gene polymorphism is associated with ossification of the posterior longitudinal ligament

This preliminary study assessed the association between ossification of the posterior longitudinal ligament (OPLL) and the transforming growth factor β receptor type 2 (TGFBR2) gene, with autoimmune disease examined as a possible underlying factor. Twenty-one patients diagnosed with OPLL and 42 control patients without OPLL (non-OPLL) were enrolled in the study. The TGFBR2 gene, composed of one promoter and seven exons, including the 5' untranslated region and flanking introns of each exon, was sequenced. Laboratory tests, including indirect immunofluorescence, were performed to detect autoimmune antibodies. The most common types of OPLL were the continuous (n=8, 38.1%) and segmental (n=8, 38.1%) types, with the fifth cervical veterbra (C5) the most common level of cervical spine involvement (n=15, 71.4%). In addition, significant associations between 455-4T→A (p=0.007) and 571G→A (p=0.024) gene variation and OPLL were found. The 95-35C→T variation in intron 1, a previously unreported variation, was also found in all patients with OPLL. Four patients revealed positive results for autoimmune antibodies and exhibited a nucleolar pattern by indirect immunofluorescence. Of these four patients, two were diagnosed with Sjogren's syndrome. The previously reported association of 455-4T→A and 571G→A polymorphisms of the TGFBR2 gene with OPLL was confirmed in this study. In addition, the 95-35C→T polymorphism in intron 1, which to our knowledge is a novel, previously unreported, nucleotide variation, was detected in all patients. Additional functional studies are required to verify the association between OPLL and the genetic variations found in this study.