Ossification of the posterior longitudinal ligament in dizygotic twins with schizophrenia: a case report.

The pathogenesis of ossification of the posterior longitudinal ligaments (OPLL) has not been clarified. We here report dizygotic twin sisters with OPLL of the cervical spine and propose a new pathogenesis of OPLL. This is the first report of dizygotic twins with OPLL. The twins suffered from schizophrenia, which might be related to the pathogenesis of OPLL. In addition, we investigated the occurrence of OPLL in 30 patients with schizophrenia who had been admitted to a mental hospital. OPLL of the cervical spine was found in six (20%) of them, with an incidence almost five times higher than the incidence of OPLL among the general population in Japan. Schizophrenia may have a increased susceptibility to OPLL.