IL17RC and ossification of the posterior longitudinal ligament of the spine: Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis was performed using RNA extracted from peripheral blood cells (Fig. 3) and demonstrated that IL17RC mRNA levels were ~ 6-fold higher in T-OPLL patients carrying the rs199772854A mutation than T-OPLL patients with the wild-type rs199772854C site (P < 0.001).