NONGOITROUS CRETINISM is presumed to be nongenetically determined, since it usually occurs as an isolated case within a family pedigree. Recent reports of concordance for this disorder among monozygotic twins1,2 and familial instances1,3-5 lend some support toward a genetic etiology.
Twin studies would provide an excellent means of estimating the degree of genetic determination for this condition if enough reports were available. It would be helpful to know the overall concordance and discordance rates in both monozygotic and dizygotic twin pairs. Discordance for athyreosis in monozygotic twins rules against an environmental cause.6-10 Discordance in dizygous twins is less interesting and would be reported infrequently, even though its incidence might be relatively high. Reports of either discordance or concordance in dizygous twins are found only in the older literature.11-14 In these studies, however, zygosity was not proven, and the type of cretinism could not be established, since
Strickland AL, Bass JW. Nongoitrous Cretinism in Monozygotic Twins. Am J Dis Child. 1969;118(6):927–931. doi:10.1001/archpedi.1969.02100040929022
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