Previous studies have indicated that SNPs in BMP2, 4, and 9, collagen 6A1, angiotensin I converting enzyme gene, BH3 interacting domain death agonist, nucleotide pyrophosphatase, and vitamin K epoxide reductase complex subunit 1 are associated with the development of OPLL. Here, ACE is linked to ossification of the posterior longitudinal ligament of the spine.