We present clinical findings in infants from three kindreds (two Hutterite and one Mennonite) with an apparently unique, fatal disorder. The major manifestations consist of severe intrauterine growth retardation, congenital contractures, and tense skin which is easily eroded. The skin is tightly drawn over the face, giving an abnormal appearance consisting of a narrow, pinched nose, small mouth, limited jaw mobility, and ectropion (in one). One infant had first-degree hypospadias. Apart from this, there were no organ malformations and the infants did not have hydrops. Histologically, the skin showed hyperkeratosis. It is postulated that this is a tissue dysplasia and that all of the clinical effects are secondary. The disorder appears to be an autosomal recessive trait. The two Hutterite families are from different endogamous subdivisions. They are related as fourth cousins once-removed and fifth cousins in multiple ways through the six nearest common ancestors of all four parents. There are 25 founders (11 couples and three individuals) who are common ancestors. We computed the probability of joint descent of the four alleles in each pair of parents and in a sample of Alberta Hutterite couples, assuming that each of the common founders in turn was the original carrier. For an allele from one particular founder couple, there is a relatively greater probability of identity by descent for each pair of parents than on the average for other couples of the same endogamous subdivision.
Apart from isoimmunization, a number of conditions may present as hydrops fetalis and now account for a large proportion of hydropic infants. A large differential diagnosis must be considered when investigating the hydropic fetus and placenta while in utero, in the neonatal period, and at autopsy. An investigative protocol is proposed.
Many studies of embryogenesis and fate of twin pregnancies are invalidated because zygosity is not determined definitively, or is assumed on the basis of inadequate criteria. This paper briefly reviews methods of zygosity determination. It reports published results and a new series of twins in which zygosity was determined by DNA fingerprinting. Implications for methods of prenatal diagnosis of zygosity are discussed in the context of the occasional need for intervention in twin transfusion syndrome or in twins discordant for major malformations. Definitive zygosity and placental anatomy (number of chorions and amnions) is discussed as the firm substrate for studies of normal and abnormal twin development.
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