[Ring chromosome 18. 18p-/18q- -deletion-syndrome]

Ring chromosome 8 in a boy with multiple congenital abnormalities and mental retardation

A ring chromosome 8 was found in peripheral blood cells in a boy, whose chromosomes were studied because of multiple congenital anomalies. Examination of skin cells revealed a 46,XY/46,XY,8r pattern. Application of several banding techniques suggested a duplication of the most distal bands of both arms in the ring. The terminal end of 8q appeared to have been retained as could be shown by R-banding. The anaesthesia and surgery the mother underwent in the first month of her pregnancy is considered as a possible cause of the chromosome abnormality.

The 18 p-syndrome. Report of four cases

Four children, two girls and two boys, were found to have a short arm deletion of chromosome No. 18. Three of them exhibit a typical dysmorphy of the face showing retraction of the midface, broad-based, flat nose, hypertelorism, epicanthus, "carp mouth", big, protruding, and low set ears, as well as a variable number of Turner-like features, failure of growth, mental retardation, and muscular hypotonia. A newly born child, who died at 2 days of age exhibited severe brain defects of holoprosencephalic series. The clinical and cytogenetic findings are compared with the reviewed data of the 18 p deletion. The hypothesis of "gene-dosis compensation" is discussed in order to explain the variable phenotypical expression of 18 p-syndrome as there is obviously to correlation between the extent of the deficiency and the expression of malformations.

Derivative chromosomal structures from a ring chromsome 4

This report describes the results from cultured lymphocytes studied at metaphase, anaphase, and interphase from an individual with a ring chromosome 4. A ring was present in 90.1% of metaphases. Special attention was directed towards the occurrence of derivative chromosomal structures, such as partially duplicated and triplicated rings, tricentric rings, chains of 3 interlocked rings, rod-shaped chromosomes, "pulverized" rings, and others. The clinical features of the individual (small stature and impaired mental development, hypoplastic thumbs, ptosis palpebrae hypoplastic external male genitalia, abnormal dermatoglphic pattern) did not conform to a specific phenotype.