Polygenic inheritance of otosclerosis

A large family has been studied and its pedigree traced for six generations. Fifteen relatives are known to have had otosclerosis. Of these, the only six individuals who developed this disease before the age of twenty were offspring of second-cousin marriages. Other children in the extended family developed the disease later and may have had somewhat less severe symptoms. The original hypothesis that the severe, early onset cases occurred among those homozygous for a monogenic trait became improbable on mathematical analysis. We conclude that the inheritance of otosclerosis in this family is polygenic and probably multifactorial. Individuals marrying within the family have a greatly increased risk of giving birth to children who will develop otosclerosis early, and perhaps severely. Those who marry outside the family have a greatly decreased risk. They do, of course, have a higher risk than the general population of having children who will at some point experience a conductive hearing loss.