[Genetic study of ossification of the spinal ligaments -hereditary factors for ankylosing hyperostosis (author's transl)].

There has been no report concerning genetic investigation of ankylosing hyperostosis (AH). This is to report the influence of hereditary factor for AH on seventeen probands and fourty-two relatives of sixteen AH families. 1) In the AH families ossifications of the yellow ligament (OYL), posterior longitudinal ligament (OPLL), and supraspinous ligament (OSSL) were more frequently observed roentgenographically in or around the spine, than in the control group. There were 32 cases with OYL, 8 with OPLL and 29 with OSSL among the total of 59 cases. Especially OYL and OSSL were frequently seen even in such younger cases as aged thirties. 2) There were 6 families in which the sibships of probands were able to be examined. Eleven of 15 cases or more than one-half of the sibships were affected by AH in the 6 families. Fourteen out of 15 had some ossifications of the spinal ligament. 3) In this series, Hahn's groove of the vertebral body was observed in 44 out of 59 members. Hahn's groove is presumed to be a causative factor of AH, which we have already reported, and is rarely encountered in normal persons after the age of 20. These results suggest that there exists a genetic diathesis of ossification of the spinal ligaments and a tendency of heredity of ankylosing hyperostosis.