Interstitial deletion of the long arm of chromosome 6 associated with unusual limb anomalies: report of two new patients and review of the literature.

We report on unusual manifestations in 2 unrelated children with interstitial deletion of 6q, with nearly identical breakpoints of 6q16.2q23.1 and 6q16.3q22.3. Major findings include growth retardation, profound developmental delay, microcephaly, facial anomalies, sparse hair, congenital heart defects, and striking hand malformations. Discordant anomalies were duodenal atresia and hypoplastic genitalia in 1 child. Split-hand defect, polydactyly, gastrointestinal anomalies, and ectodermal dysplasia have not been described previously in children with 6q deletion. The presence of hand malformations in 2 children with similar deletion breakpoints strongly suggests that this is a candidate region for one or more genes involved in limb development. Comparison of the clinical findings of other patients with 6q2 deletion suggests a recognizable phenotype.

Deletion of chromosome 11 and of 14q sequences in neuroblastoma.

Restriction fragment length polymorphism (RFLP) analysis carried out on 45 primary neuroblastomas showed deletion of chromosome 11 sequences in 12 of 37 (32%) informative cases. Both 11p and 11q probes were informative in seven tumors; loss of all of chromosome 11, of only 11p sequences, and of only 11q sequences was observed in 4, 1, and 2 tumors, respectively. A cytogenetic abnormality involving translocation of chromosome arm 11q to chromosome arm 1p was observed in a primary tumor. Deletion of 14q was observed in 6 of 27 (22%) informative cases. Deletion of chromosome 11 but not 14q may correlate with regional and metastatic disease. These results suggest a possible role for sequences localized to chromosome 11 and to 14q in the development and/or progression of neuroblastoma.

Characterization of i(18p) in prenatal diagnosis by fluorescence in situ hybridization.

A case is presented in which chorionic villus direct preparation and cultured chorionic villus cells revealed a 47,XX+mar karyotype. The marker was a small metacentric chromosome and appeared to be i(18p)--isochromosome 18p. Follow-up studies in both amniotic fluid and fetal fibroblasts confirmed the karyotype. In order to characterize the marker, a panel of biotinylated DNA probes was used, including a whole chromosome 18 probe, chromosome 18-specific alpha satellite DNA, Yac clones, and a pan-telomeric probe. These studies show that the marker is a monocentric i(18p) in which about 80 per cent of chromosome 18 alpha satellite DNA has been lost.

Cytogenetic analysis of 39 pediatric central nervous system tumors.

Consistent cytogenetic abnormalities have been described in many pediatric solid tumors, including Ewing's sarcoma, Wilms' tumor, and neuroblastoma. Similar analysis of pediatric central nervous system (CNS) tumors has been hampered by technical problems. We report chromosome results from 39 pediatric CNS tumors. Abnormalities of chromosome 17 were noted in 3 of 11 primitive neuroectodermal tumors (including i(17q) in 2 tumors), confirming data observed by other investigators. Cells from 2 of 11 primitive neuroectodermal tumors (PNET) exhibited loss or structural abnormalities involving chromosome 11. Loss or distal deletion of chromosome 7q was noted in cells from two PNETs. Because other investigators have shown loss of heterozygosity on 17p in about one-third of PNET, we propose that chromosome regions 7q and 11 are areas worthy of further study in pediatric PNET. Numerical abnormalities were noted in 6 of 21 astrocytomas. Hyperdiploidy was demonstrated in 1 of 4 pilocytic astrocytomas and pseudopolyploidy was demonstrated in 4 of 13 anaplastic astrocytomas. Structural chromosome abnormalities (translocations, deletions) were noted in 4 of 13 anaplastic astrocytomas. Complex structural anomalies were observed in one craniopharyngioma. A rhabdoid tumor of the brain exhibited multiple complex structural rearrangements but did not exhibit the monosomy 22 observed in some rhabdoid tumors. Hypodiploidy and loss of chromosome 22 were noted in a clinically aggressive meningioma, corroborating observations by other investigators.

Establishment of a rhabdoid tumor cell line with a specific chromosomal abnormality, 46,XY,t(11;22)(p15.5;q11.23).

The malignant rhabdoid tumor is a rare, poorly understood tumor which occurs primarily in children. The kidney is a frequent primary site of origin, but the tumor has arisen in other mesodermally derived tissues as well. Controversy exists regarding the embryonic origin of the rhabdoid tumor and recent histopathologic studies suggest that it may be of neuroepithelial origin. Our immunohistochemical and electron micrographic studies support this theory. No consistent chromosome abnormalities have been reported in this tumor and no cell lines are available for study. We have established and characterized the first rhabdoid tumor cell line. It possesses a specific chromosomal abnormality, 46,XY,t(11;22)(p15.5;q11.23). The translocation may provide an important clue to the pathogenesis of the tumor as well as an opportunity for further study of the involved chromosome regions.

Rothmund-Thomson syndrome associated with trisomy 8 mosaicism.

This report describes a boy with Rothmund-Thomson syndrome associated with trisomy 8 mosaicism. The patient presented with typical features of Rothmund-Thomson syndrome but some of the features often seen in trisomy 8 mosaics were also observed in him. The possibility that the two disorders might share a common pathogenesis is postulated.

A patient with an interstitial deletion of the proximal portion of the long arm of chromosome 4.

A patient with a proximal deletion of the long arm of chromosome 4 is presented. This patient and 6 others previously described appear to have similar findings of moderate to severe developmental delay, small size, small hands and feet, and similar facial appearance. These patients appear to be quite different from those with more distal 4q deletions.

Triple X chromosome constitution and acute nonlymphocytic leukemia.

A case of acute nonlymphocytic leukemia occurring in a 15-year-old girl with a triple X sex chromosome constitution is discussed.

Acute non-lymphocytic leukemia following multimodality therapy for retinoblastoma.

The genetic form of retinoblastoma carries a high risk of secondary malignant neoplasm, apparently not related to the use of chemotherapy. A child with unilateral non-genetic retinoblastoma who had received chemotherapy and radiation therapy and developed acute non-lymphocytic leukemia (ANLL) is reported. The occurrence of ANLL and retinoblastoma has not been previously reported.

Identification of a case of Y:18 translocation using a Y-specific repetitive DNA probe.

We have used a recombinant DNA clone derived from the Y-specific 3.4-kb repeats for in situ chromosome hybridization and Southern blotting analysis to identify a case of de novo Y;18 translocation. The proband has a chromosome complement of 46,XY and a variant chromosome 18 with a Q-bright and C-positive short arm. The father has a normal male karyotype of 46,XY. The mother has a female karyotype of 46,XX and an unusually large Q-bright satellite on one chromosome 22. In situ hybridization with the 3.4-kb probe to the metaphase preparations of family members indicated that the additional Q-bright material in the proband's variant chromosome 18 derived from the Y chromosome of his father, and not from the variant chromosome 22 of his mother. On Southern hybridization, the proband had approximately twice the amount of 3.4-kb repeats per cell as his father. These observations suggest a de novo genetic rearrangement in the proband which probably occurred during the father's spermatogenesis.

De novo interstitial deletion in the long arm of chromosome 9: a new chromosome syndrome.

An infant with an interstitial deletion 46,XY, del(9)(pter leads to q22::q32 leads to qter) is described. Clinical features included abnormal craniofacies with hypotelorism, narrow palpebral fissures, sclerocornea, deep vertical groove, and supraorbital ridge hypoplasia. There was unilateral preaxial polydactyly and toe syndactyly. Generalised hirsutism was noted. The infant had surgery for duodenal atresia but died at the age of 3 months. Unilateral renal dysplasia and accessory spleens were found at necropsy.

Cytogenetic anomalies in a patient with ataxia, immune deficiency, and high alpha-fetoprotein in the absence of telangiectasia.

A 58-year-old male with spinocerebellar degeneration in association with choreiform movement is described. He possessed neurological, biochemical, immunological, as well as cytogenetic disorders predisposing to cancer to patients with ataxia telangiectasia (AT). Cytogenetic abnormalities included four abnormal clones: trisomy 14;t(13;14);t(7;14)(q32;q12); and t(7;14)(p13;q12), in addition to breaks, rings, and acentric chromosomes. The absence of telangiectasia, the late onset of neurological symptoms, and the prolonged survival in this case may separate it from the classic AT. Although the syndrome may be recognized as a new chromosome instability syndrome, multiple allelism may play a role in the expression of a milder form of AT.

Gonadal dysgenesis with 45,X/46,X,dic(Yp) mosaicism.

A female patient with a gonodal mucinous cystadenoma on the right side and a gonadoblastoma on the left was found to be a 45,X/46,X,dic (Yp) mosaic. This brings the total number of cases with dicentric Y chromosome reported to date to 23. Together with the available evidence, the information derived from this case supports the hypothesis that the gene on the long arm of the Y chromosome is responsible for the initiation of testicular differentiation, whereas that on the short arm is responsible for the maturation of the testes.