There are many questions unanswered about otosclerosis related to its different incidences between races; to its mode of inheritance; to the possibillity of abnormal karyotypes. The authors conducted chromosomal studies in 15 Japanese otosclerotic patients, 9 female and 6 male, ranged in age from 20 to 62 years, including 7 familial otosclerosis from 3 different families and 8 sporadic cases. In 11 patients the diagnosis was confirmed during operation, and in 4 it was confirmed by the audiometric batteries. The preparations for karyotype examinations were made using a short-term culture of peripheral blood, and about 25-50 suitable cells in metaphase were photographed and examined. And the the results are as follows:
1) Normal karyotypes were demonstrated in all male patients (46, XY) and all but one female (46, XX), and there was no mosaicism, trisomy or tetrasomy contended previously by J. M. Tato et al. in 1963.
2) A 24-year-old female patient, apparently normal and with regular menstrual periods but slightly retarded mentality, was found to have 47 chromosomes with one extra X-chromosome in all 20 cells examined. Sex chromatin bodies in the nuclei of the epithelial cells from buccal mucosa were also examined and 34% of the nuclei contained two X-chromatin bodies, and this woman was diagnosed as Triple-X female (47, XXX). Her mother was also diagnosed as having otosclerosis but her karyotype was normal.
3) Reviewing the literature, Triple-X females can have a variety of physical anomalies, but no deafness or otosclerosis have been reported. The patient, therefore, was judged to possess 47, XXX karyotype accidentally accompanied with otosclerosis.
4) In conclusion to this present study, there is no evidence of karyotype abnormality characteristic to Japanese otosclerotic patients.