Apparently non-deleted ring-1 chromosome and extreme growth failure in a mentally retarded girl

Abstract

A girl who was the product of the 1st recognized conception by healthy and chromosomally normal parents, and who was born 5 wk before term with a birth weight of 1690 g, was found to have a ring-1 chromosome, r(1), in almost all cells analyzed. A minor proportion of cells had a normal diploid chromosome complement including 2 regular no. 1 homologs. A few cells contained a large dicentric ring, and 2 monocentric r(1) chromosomes were simultaneously observed in a few other cells. Q[quinacrine]- and G[Giemsa]-banding revealed the r(1) chromosome to be apparently non-deleted. The patient phenotypically resembled the 3 previously described human subjects with r(1) chromosomes, especially with respect to her remarkable growth failure and mental retardation. From consideration of data available on general development in subjects with an autosomal ring chromosome, the presence of such a ring chromosome per se in an early fetal chromosome complement may predispose to significantly retarded intrauterine and postnatal growth. Various genetic implications, including mitotic irregularities with subsequent loss of cells at division, apparently account for the significant reduction of body mass in these patients.