Ring chromosome 22 and autism: report and review

Ring chromosome 22 has been described in over 50 cases. A characteristic phenotype has not been fully delineated; however, long face, thick eyebrows, 2-3 toe syndactyly, mental retardation, adequate somatic growth and the absence of major malformations are noted in many cases. An 11-year-old boy with ring chromosome 22 and 46,XY,r(22)(p11.31-q13.31 approximately q13.33) karyotype presented with global developmental delay, autistic disorder, and dolichocephaly, apparently low-set and large ears, midface hypoplasia, and 2-3 toe syndactyly. This is the second report of a ring chromosome 22 with autistic disorder. There appears to be an association between abnormalities of chromosome 22, including r(22), and autistic disorder; however, this occurrence may be a result of the association of autistic disorder with mental retardation rather than specifically due to r(22). The physical findings in this case also suggest that ring chromosome 22 causes a subtle but distinct phenotype which has previously been proposed.

Partial tetrasomy with triplication of chromosome (5) (p14-p15.33) in a patient with severe multiple congenital anomalies

We report on a newborn infant with a de novo triplication of the distal segment of 5p: 46,XX,trp(5) (pter-->p14::p14-->p15.33::p15.33--> qter) and multiple congenital anomalies consistent with triplication of 5p. Partial triplication was documented by fluorescence in situ hybridization with a cosmid probe specific for 5p15.2 and microdissected probes obtained from "5pter." Partial duplication of the short arm of chromosome 5 is associated with a specific phenotype that appears to be dependent on the chromosomal region duplicated. Duplication of 5p with breakpoints proximal to band p14 is generally associated with distinct craniofacial malformations, cardiac, renal, intestinal, and limb defects, and mental retardation, whereas duplications with breakpoints distal to 5p14 result in a milder phenotype characterized by minor facial anomalies, developmental delay, and seizures. The most proximal breakpoints of the partial triplication in this patient was estimated to be 5p14, suggesting that a more severe phenotype can occur with triplication of the more distal segment.

Deletion 3q in two patients with blepharophimosis-ptosis-epicanthus inversus syndrome (BPES)

BACKGROUND

Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) is an autosomal dominant condition mapped to chromosome 3q23. There are several reports of chromosomal abnormalities involving this region with a resultant phenotype that includes BPES.

METHOD

We reassessed two unrelated boys ages 3 and 5 with BPES and associated nonocular abnormalities. Karyotype, which had been previously reported as normal, was repeated using high-resolution banding techniques, to look specifically at 3q23. Clinical findings were tabulated and compared with previously reported cases.

RESULTS

Both patients proved to have interstitial deletions of chromosome 3, the first involving bands q22.2q25.1 and the second q22.2q24. The first patient exhibited prenatal and postnatal growth retardation, with global developmental delay, while the second patient had normal growth and development except for speech delay. Both had dysmorphic facies with BPES, flat philtrum, a thin upper lip, and small chin. In addition, the first boy had an inguinal hernia and hypospadius; the second boy had abnormal auricles and metatarsus adductus. The eight cases of interstitial deletions of 3q2 and six rearrangements involving this region have a remarkably similar phenotype.

CONCLUSIONS

Deletion of 3q23 is a recognizable contiguous gene syndrome. Microdeletions of 3q23 should be ruled out in any sporadic case of BPES especially if there are associated nonocular abnormalities.

Deletion 4q21/4q22 syndrome: two patients with de novo 4q21.3q23 and 4q13.2q23 deletions

We report on 2 patients with de novo proximal interstitial deletions of the long arm of chromosomes 4: in one the deletion resulted in monosomy (4)(q21.3q23), in the other it produced monosomy (4)(q13.2q23). Review of 9 cases of deletions involving the 4q21/4q22 region reported previously detected a characteristic phenotype in 8 patients. This phenotype was present in our patients. We conclude that the deletion in the 4q21/4q22 region results in a specific clinical syndrome associated with central nervous system overgrowth that may be a result of anomalous imprinting in the 4q21/4q22 region.

Tissue-specific methylation differences and cognitive function in fragile X premutation females

Tissue-specific variation in (CGG)n repeat size and methylation status of the FMR1 gene was investigated in 17 female premutation carriers. Minor variation in premutation repeat size among leukocyte, lymphoblast, and fibroblast tissues was noted in some subjects. One subject exhibited a premutation size allele of (CGG)64 in leukocyte and fibroblast tissues by polymerase chain reaction analysis but a normal-size allele of (CGG)46 in lymphoblast cells, suggesting low-level mosaicism in blood and clonality of the lymphoblast cell line. Six subjects exhibited differences in methylation pattern between leukocytes and lymphoblasts but not between leukocytes and fibroblasts, whereas 2 subjects showed large differences in methylation pattern between leukocytes and fibroblasts. Cognitive function was studied in 14 subjects using the Wechsler Adult Intelligence Scale-Revised. Mean Verbal and Performance IQs were well within the average range as was the mean Full Scale IQ; nevertheless, a trend toward lower Performance IQ compared with Verbal IQ was observed. No significant correlation was apparent between Full Scale IQ and (CGG)n repeat size; however, a significant positive correlation was observed between Full Scale IQ and the proportion of the active X carrying the normal FMR1 allele in fibroblasts but not in leukocytes or lymphoblasts.

Terminal deletion of the long arm of chromosome 3 [46,XX,del(3)(q27-->qter)]

We report on a terminal deletion of the long arm of chromosome 3 [46,XX,del(3)(q27-->qter)] in a female newborn infant who died 45 hours after delivery and had multiple congenital abnormalities including bilateral anophthalmia, congenital heart disease, and abnormal genitalia. The findings are compared to those of four previously reported cases with terminal del (3q).

Molecular analysis of three patients with interstitial deletions of chromosome band 14q31

Two patients and one three generation family with interstitial deletions of distal chromosome band 14q31 are described. The deletions were initially identified by chromosome analysis; we have used highly informative simple sequence repeat polymorphisms to define the deletions at the molecular level. This analysis also establishes the parental origin of the deleted chromosome. One of the patients was initially described as having a terminal deletion of chromosome 14 from 14q31 to 14qter; we show here that this child has instead an interstitial deletion of band 14q31. The smallest deletion involves a single anonymous DNA marker and is associated with an almost normal phenotype. The two patients with larger deletions have phenotypes similar to those seen in previously described cases of interstitial deletions of chromosome 14, including minor dysmorphic features and developmental delay. Delineation of these deletions allows the ordering of markers within the 14q31 region, in which the gene for the degenerative neurological disorder Machado-Joseph disease is localised.

Molecular analysis redefines three human chromosome 14 deletions

We have used a panel of 13 DNA markers in the distal region of chromosome 14q to characterize deletions in three patients determined cytogenetically to have a ring or terminally deleted chromosome 14. We have characterized one patient with a ring chromosome 14 [r (14) (p13q32.33)] and two with terminal deletions [del (14) (pter-->q32.3:)]. The two patients with cytogenetically identical terminal deletions of chromosome 14 were found to differ markedly when characterized with molecular markers. In one patient, none of the markers tested were deleted, indicating that the apparent terminal deletion is actually due to either an undetected interstitial deletion or a cryptic translocation event. In the other patient, the deletion was consistent with the cytogenetic observations. The deleted chromosome was shown to be of paternal origin. The long-arm breakpoint of the ring chromosome was mapped to within a 350-kb region of the immunoglobulin heavy chain gene cluster (IGH). This breakpoint was used to localize markers D14S20 and D14S23, previously thought to lie distal to IGH, to a more proximal location. The ring chromosome represents the smallest region of distal monosomy 14q yet reported.

Syndrome of proximal interstitial deletion 4p15: report of three cases and review of the literature

We report on two boys and a girl with interstitial deletion in the short arm of chromosome 4 including the segment p15.2p15.33. All had normal growth with psychomotor retardation, multiple minor congenital anomalies, and a characteristic face distinct from that of the Wolf-Hirschhorn syndrome. One of the patients had congenitally enlarged penis. These patients resemble some of the previously reported patients with similar cytogenetic abnormalities and suggests the recognition of a specific clinical chromosome deletion syndrome.

Wilms tumor in a patient with Prader-Willi syndrome

The development of Wilms tumor in a patient with Prader-Willi syndrome prompted us to determine the parental origin of the genes implicated in both disorders because of the sex-specific parent-of-origin effects previously demonstrated for both conditions. A paternal chromosome 15q11-q13 deletion was demonstrated, but no changes were demonstrated in a limited analysis of chromosome 11p, which harbors two Wilms tumor suppressor genes, WT1 and WT2.

Mosaicism for duplication 12q (12q13-->q24.2) in a dysmorphic male infant

We report the clinical findings in a boy with mosaicism for a duplication of chromosome 12q13.1-->q24.2. His clinical characteristics are very similar to previously reported mosaic duplications of the distal long arm of 12, as well as several cases with non-mosaic duplications. It is proposed that this represents a clinically distinguishable syndrome for 12q duplication, in mosaic or non-mosaic form.

Craniosynostosis associated with partial duplication of 15q and deletion of 2q

We report on an infant with multiple congenital anomalies including complex craniosynostosis associated with an unbalanced karyotype, 46,XY,-2,+der(2),t(2;15)(q37;q26)pat. The previous report of a child with cloverleaf skull and partial duplication of 15q25----qter and the Man-on-Mouse Homology map suggests that a critical segment for synostosis of sutures may be in this region.

Trisomy 18 and a constitutional maternal translocation (2;18)

Parental chromosomes are usually not analyzed in cases of trisomy 18 because the extra 18 is assumed to have arisen through a meiotic nondisjunctional event. We report on a case of a trisomy 18 and a maternal translocation (2;18)(q34;q12).

Canadian multicenter randomized clinical trial of chorion villus sampling and amniocentesis. chromosome mosaicism in CVS and amniocentesis samples

Data on 1040 chorionic villus and 969 amniotic fluid samples were collected from women studied in the Canadian Multicentre Randomized Clinical Trial of Chorion Villus Sampling and Amniocentesis. Cytogenetic results were obtained from 98.0 per cent of chorionic villus samples and from 99.9 per cent of amniotic fluid samples. Level I mosaicism (a single cell with an abnormal karyotype) occurred frequently in both chorionic villus and amniotic fluid samples and appeared to have no clinical significance. Level II mosaicism occurred in 0.9 per cent of CVS mesenchyme and 1.5 per cent of amniotic fluid cultures and in general was not perceived to be of sufficient concern to warrant cytogenetic follow-up studies. Level III mosaicism was reported in 18 CVS cases (15 cytotrophoblast, 1 mesenchyme, and 2 with both cell methods) and in one amniotic fluid case. In all cases but one (fetus with trisomy 18), level III mosaicism was confined to the placenta. Maternal cell contamination occurring with a frequency of 6.4 per cent in the mesenchyme analyses was a concern. This study supports the final report of the Canadian Multicentre Randomized Clinical Trial of Chorion Villus Sampling and Amniocentesis. Cytogenetic analysis of chorionic villus samples appears to be an acceptable alternative to the analysis of amniotic fluid samples. However, because of mosaicism and maternal cell contamination concerns, the examination of both cytotrophoblast preparations and mesenchyme cultures from chorionic villus samples is recommended.

Characterization of malignant peripheral blood cells of juvenile chronic myelogenous leukemia

Characterization studies were performed on the malignant peripheral blood cells from three patients with juvenile chronic myelogenous leukemia (JCML) by allowing the cells to increase numerically in liquid cultures. JCML cells proliferated rapidly and excessively in the absence of an added humoral growth factor, whereas control peripheral blood cells declined in number when cultured under identical conditions. Clonality of JCML cells was proven by cytogenetic analysis of the proliferating population. JCML cells were exclusively of monocytic lineage as determined by morphology, staining characteristics, and monoclonal antibody identification of cell-specific surface antigens, but cytochemical and functional studies identified aberrant properties indicating defective differentiation. Striking differences from control cells in ultrastructure and topography were also observed by transmission and scanning electron microscopy. These data provide new information on the cellular origin of JCML and form the basis for further study of leukemic cell biology in this disease.

A dominantly inherited cytogenetic anomaly: a possible cell division mutant

Short-term lymphocyte cultures from three unrelated patients showed an increased frequency of mitoses with separated centromeres and splayed chromatids in the presence of colcemid. We refer to this phenomenon as premature centromere division (PCD). In two of the three patients the frequency of PCD in lymphocytes decreased when colcemid was omitted prior to harvest but was still higher than controls, whereas in the third patient, the frequency appeared unchanged. Cultured fibroblasts from the latter patient exhibited increased tetraploidy and multinucleated cells. Transmission of the trait in the three families was compatible with autosomal dominant inheritance. Time lapse cinemicrographic studies on fibroblasts from one patient demonstrate a shortened metaphase time, suggesting that the separation of chromatids observed in this patient may indeed be premature. The nature of the mutation(s) and phenotype correlation if any is unknown.

The association of a lymphoreticular malignancy with an 11q deletion: a coincidence or a cancer susceptibility?

A balanced paternal chromosome insertion, ins(11) p14q14q21, resulted in a female with an unbalanced karyotype, del(11)(q14q21). This imbalance presumably arose from a meiotic crossover between the breakpoint of the insertion and the breakpoints of the deletion. This child developed a malignant lymphoma of the thymus in the first year of life. The association of a lymphoma with an 11q deletion may not be a coincidence in view of the frequent involvement of 11q in cytogenetic alterations of lymphomas.