Walter E. Nance

The implementation of universal screening programs to detect hearing defects in newborns has dramatically increased the identification of hearing loss in infants. Recent advances in understanding the nature and causes of prelingual hearing loss, combined with advances in technology, suggest that further improvement in these programs can readily be achieved.

This investigation was undertaken to evaluate possible genetic determinants of bone mass with the premise that inheritance of bone mass could be of etiologic importance in osteoporosis. Bone mass and width measurements were made with the photon absorption technique on the right radius of 71 juvenile and 80 adult twin paris. The variance of intrapair differences of bone mass in monozygotic (MZ) juvenile twins was 0.0013 g(2)/cm(2) compared to 0.0052 g(2)/cm(2) in the dizygotic (DZ) twins. For the adult twins the variance of intrapair differences in bone mass was 0.0069 for MZ and 0.0137 for DZ twins. Similar results were obtained for bone width. The significantly larger variation in intrapair differences in DZ twins indicates that these traits have significant genetic determinants. These intrapair differences were found to increase with age, suggesting that genetic-environmental interaction also contributes to the observed variation in bone mass. These data provide evidence that bone mass does have significant genetic factors, which alone or in conjunction with environmental factors may predispose persons to the development of osteoporosis.

Profound, early-onset deafness is present in 4-11 per 10,000 children, and is attributable to genetic causes in at least 50% of cases. Family history questionnaires were sent to 26,152 families of children with profound, early-onset deafness not known to be related to an environmental cause. The probands were ascertained through the 1988-89 Gallaudet University Annual Survey of Hearing Impaired Children and Youth. The analysis is based on the responses that were received from 8,756 families. Classical segregation analysis was used to analyze the family data, and to estimate the proportions of sporadic, recessive and dominant causes of deafness in the families. These data were consistent with 37.2% of the cases due to sporadic causes, and 62.8% due to genetic causes (47.1% recessive, and 15.7% dominant). An earlier study using the 1969-70 Annual Survey found 49.3% sporadic cases and 50.6% genetic, demonstrating that the proportion of sporadic cases of early-onset deafness has significantly decreased since 1970.