Familial mental retardation in a family with an inherited chromosome rearrangement

Partial trisomy 4 resulting from a complex maternal rearrangement of chromosomes 2, 4, and 18 with interstitial translocation

A woman presented a complex chromosome rearrangement with translocation between chromosome 2 and 4 in addition to an insertion of the band 4q12 leads to q13 in the long arm of chromosome 18. The authors present a case study of the daughter who displayed the abnormal chromosome 18 and trisomy of band 4q12 leads to q13.

Syndromes associated with deletion of the long arm of chromosome 18[del(18q)]

We studied eight persons whose karyotypes demonstrated deletion of a portion of the long arm of chromosome 18. Seven of these persons who showed the typical del(18q) syndrome had a common deletion in band 18q21, most likely band q21.3, and in at least two persons the deletion was interstitial. Another mentally retarded child, dissimilar in appearance, had a more proximal deletion within band 18q12. Two different clinical syndromes resulted from deletions of these different segments of the long arm of chromosome 18.

Familial, balanced insertional translocation of chromosome 7 leading to offspring with deletion and duplication of the inserted segment, 7p15 leads to 7p21

We report an uncle and niece with duplication and deletion, respectively, of segment 7p15 leads to 7p21 originating from a balanced, intrachromosomal insertion in their mothers. The proposita had prenatal and postnatal growth deficiency, retarded psychomotor development, microcephaly, wide cranial sutures, ocular hypertelorism, small palpebral fissures, apparently low-set and malformed ears, cleft palate, congenital heart defect, hypoplasia of the distal phalanx of first fingers, rocker-bottom feet, persistent cloaca, and imperforate anus. She died at three months. Her maternal uncle has duplication of this segment and is alive at 32 years. He has severe mental deficiency, but normal growth; communicating hydrocephalus was diagnosed at three months.

Partial trisomy 18q in a newborn with typical 18 trisomy phenotype

This paper describes a case of partial trisomy of almost the entire long arm of chromosome 18 in a newborn with classic trisomy-18 phenotype, resulting from a de novo unbalanced 181/21p translocation: karyotype: 46,XX,-21,t(18;21)(18qter leads to 18q11 ::21p12 leads to 21qter). A review of the other reported cases of partial trisomy 18 suggests that a critical segment in chromosome 18, corresponding to bands q11-q12, might be responsible for most of the signs of trisomy 18, including failure to thrive and early death.

Segregation of an insertional chromosome rearrangement in 3 generations

The interstitial deletion of a segment of chromosome 13, 13q21 leads to 13q22, and its inversion and insertion into the long arm of chromosome 3 at breakpoint q12, was found to segregate in 3 generations of a family. Segregation of this 3 break rearrangement gave rise to individuals monosomic, trisomic, or balanced for the involved segment. Monosomy for 13q21 leads to 13q22 was associated with mental retardation, expressive aphasia, microcephaly, hand abnormalities, and short stature. Partially trisomic individuals had normal mentality, extremely high arched palate, and mild dysmorphic features. There was no evidence for retinoblastoma in the individuals examined. The balanced carriers were normal. Comparison of monosomic individuals with one previous report of a similar deletion reveals marked phenotypic similarities.

A cytogenetic survey of 14,069 newborn infants. I. Incidence of chromosome abnormalities

Data from a chromosome examination of 14,069 consecutive newborn infants is presented. Successful karyotypes were obtained on 13,939 babies using short-term blood cultures and conventional staining methods. Of those, 13,645 babies had normal chromosomes; 64 (0.46%) had a major chromosome abnormality; and 230 (1.65%) had a marker chromosome; giving a total of 294 (2.11%) babies with a major chromosome abnormality or distinctive marker chromosomes. Six male babies with sex chromosome abnormalities had a 47,XXY and four a 47,XYY karyotype, and three were mixoploids. Five female babies had a 47,XXX karytotype and two were mixoploids. There were three babies with ambiguous external genitalia, all with normal karyotypes. Fourteen babies had 21-trisomy; there were three 18-trisomics and one 13-trisomic. The mother of one 18-trisomy baby had a balanced (18;21) translocation. Twenty-four infants had a balanced chromosome rearrangement. Eleven of these were reciprocal and thirteen were Robertsonian translocations. One baby had an unbalanced derivative chromosome resulting from an 18;11 insertion. Two infants with additional unidentified fragments were detected. Two hundred and thirty babies (1:60) carying distinctive chromosome variants were detected. The commonest variant was the Yq+ among males (0.89%). Other common variants involved the short arms of the D and G groups (0.32% and 0.57%, respectively) 16q+ (0.09%), and 1q+ (0.04%). The results of the present study when combined with five other comparable studies, thus comprising a total of 46,150 newborn infants, indicates that the frequency of major chromosome abnormalities is between 1:150 and 1:200 live-born babies. This represents a small proportion of all conceptuses with chromosome abnormalities, which has been estimated as being approximately 1:20. It is thus clear that chromosome abnormalities form a major part of the genetic load carried by the human population. The development of chromosome banding techniques already has increased, and with further increase, the complexities of human cytogenetics and may reveal many additional rearrangements undetectable by conventional methods.

The human complement after trypsin pretreatment as compared to the Paris standard

A composite G-banding diagram after trypsin pretreatment of metaphase chromosomes from 5 different individuals (2 males and 3 females) is presented and compared with the Paris diagram. The patterns obtained by the present technique were very similar to those previously reported. It was found that the darkly staining bands were much more consistent in appearance than the lightly staining bands and that there was little individual variation.