YUMITA, S., FURUKAWA, Y., SOHN, H.E., UNAKAMI, H., MIURA, R. and YOSHINAGA, K. Familial Idiopathic Hypoparathyroidism and Progressive Sensorineural Deafness. Tohoku J. exp. Med., 1986, 148 (2), 135-141 - Three cases from two families with idiopathic hypoparathyroidism and progressive sensorineural deafness are described. Cases 1 and 2 were siblings. Case 3 was one of four siblings from another family. All of them had both idiopathic hypoparathyroidism and progressive sensorineural hearing loss. There was no evidence to suggest involvement of autoimmune mechanism in these cases except for the associated Graves' hyperthyroidism in case 3. Human leukocyte antigen A9 and A11 were positive in both families. The sensorineural hearing loss was progressive even after the treatment for hypoparathyroidism. As the familial idiopathic hypoparathyroidism is a very rare entity, it is unlikely that this disease is associated with familial progressive sensorineural deafness by chance. The combination of these two diseases may compose a new syndrome.