Infantile hypertrophic pyloric stenosis: data on 81 pairs of twins.

Abstract

Summary87 affected twins (in 81 pairs) were identified among 3,982 children with pyloric stenosis. The proportion of twins among affected (1 in 46) is about the same as in the general population of births. The incidence of pyloric stenosis in partners of affected twins is 8.6 per cent, considerably higher than in the general population of births (0.3 per cent) but only slightly higher than in subsequent sibs (5.8 per cent).The frequency of concordance is about the same in MM (4 of 31) and MF (2 of 23) pairs. Of 39 like sexed pairs 4 were concordant; the expected number of monozygotic pairs is 18 (assuming the usual proportion of monozygotic pairs), which suggests that the frequency of concordance among them is not greater than 4 in 18. It is shown that the distribution of MM, FF and MF pairs in the series corresponds closely to the distribution expected in a twin universe which contains the usual proportions of monozygotic and dizygotic twin pairs.