Ossification of the posterior longitudinal ligament of the spine.

"The Japanese disease" or ossification of the posterior longitudinal ligament of the cervical spine was initially thought to affect only the Japanese people. Non-Japanese Asian and Caucasian cases have been reported but appear to be exceedingly rare. The reason is unknown. Although the disease appears to be generally benign, it can cause a myelopathy. We present here 16 non-Japanese patients in Singapore who were found to have ossification of the posterior longitudinal ligament in the cervical, thoracic and lumbar spine.