Clinical, cytogenetic and molecular characterization of two cases of mosaic ring chromosome 13.

The occurrence of mosaic ring chromosome 13 is rare. The mechanism of ring chromosome formation is usually associated with loss of genetic material. We report 2 cases of mosaic ring chromosome 13, resulting in deletion of 13qter. The first patient, a 15 year-old boy, presented a delayed psychomotor development, mental retardation, dysmorphic features and bleeding disorders associated with a de novo terminal 13q34 deletion. The second case was a foetus of 31 weeks with prenatal diagnosis of severe malformation such as holoprosencephaly, congenital cardiac defects, gastro-intestinal abnormalities with intrauterine growth retardation, the molecular analysis showed a de novo deletion encompassing the region 13q31.3-q34.

[Fish and chips]. / Fish and chips.

Academic hospital laboratories should offer patients the possibility to have the most accurate diagnosis by the development of new analyses, such as molecular biology tests including FISH (Fluorescent In Situ Hybridization) and chips (microarrays,...). The purpose of this article is to describe the principles and the potential applications of these techniques.

Deletion of Xpter encompassing the SHOX gene and PAR1 region in familial patients with Leri-Weill Dyschondrosteosis syndrome.

Heterozygote deletions or mutations of pseudoautosomal 1 region (PAR1) encompassing the short stature homeobox-containing (SHOX) gene cause Leri-Weill Dyschondrosteosis (LWD), which is a dominantly inherited osteochondroplasia characterized by short stature with mesomelic shortening of the upper and lower limbs and Madelung deformity of the wrists. SHOX is expressed by both sex chromosomes in males and females and plays an important role in bone growth and development. Clinically, the LWD expression is variable and more severe in females than males due to sex differences in oestrogen levels. Here, we report two familial cases of LWD with a large Xp terminal deletion (approximately 943 kb) of distal PAR1 encompassing the SHOX gene. In addition, the proband had mental retardation which appeared to be from recessive inheritance in the family.

Precocious puberty associated with partial trisomy 18q and monosomy 11q.

We report a 10-years-old female patient with a partial trisomy 18q and monosomy 11q due to a maternal translocation. The phenotype of our proband is partially common with Jacobsen syndrome and duplication 18q but she has also some atypical anomalies such as precocious puberty, a retinal albinism and hypermetropia. Based on cytogenetics and FISH analysis, the karyotype of the proband was 46,XX,der(11)t(11;18)(q24;q13). To the best of our knowledge, this is the first report of precocious puberty associated with either dup(18q) or del(11q) syndromes.

Major decrease in the incidence of trisomy 21 at birth in south Belgium: mass impact of triple test?

In South Belgium (Wallonia), the 'triple test' was introduced in 1990-1991, and is nowadays a widely accepted screening method for assessment of trisomy 21 risk in pregnancy. The 'triple test' is not regulated and can be freely performed by any biomedical lab, making epidemiological data unavailable. By contrast, cytogenetic investigations are limited to a few genetic centres, and accurate statistics can be easily built from their files. During the period 1984-1989, a total of 244 trisomy 21 (1/876 pregnancies) were diagnosed in the Genetic Centres of Liège and Loverval, 42 (17%) of them prenatally. During the period 1993-1998, 294 trisomy 21 (1/704 pregnancies) were observed, 165 (56%) of which prenatally, and more than 90% of affected pregnancies were terminated. Even after correction for late foetal loss of trisomic foetuses, the difference is highly significant, and corresponds to a theoretical shift in the incidence of trisomy 21 at birth from 1/794 to 1/1606. As no remarkable progress occurred in other non-invasive prenatal screening procedures or general health care policies in Belgium, the most reasonable explanation is the use on a large scale of triple test by pregnant women, and the election of termination for most affected pregnancies.

Private multiple congenital anomaly syndromes may result from unbalanced subtle translocations: t(2q;4p) explains the Lambotte syndrome.

In 1990, Lambotte syndrome was reported as an apparently autosomal recessive multiple congenital anomaly/mental retardation (MCA/MR) syndrome observed in 4 of 12 sibs from a probably consanguineous mating [Verloes et al., Am J Med Genet 1990; 37:119-123]. Major manifestations included intrauterine growth retardation (IUGR), microcephaly, large soft pinnae, hypertelorism, beaked nose, and extremely severe neurologic impairment, with holoprosencephaly in one instance. After the observation of a further affected child born of one unaffected sister, in situ hybridization analysis and chromosome painting techniques demonstrated a subtle t(2;4)(q37.1; p16.2) translocation in the mother, suggesting a combination of 2q/4p trisomy/monosomy in all of the affected children of the family. Many private sporadic or recurrent MCA/MR syndromes maybe due to similar symmetric translocations, undetectable by conventional banding techniques.

Monosomy 11q: report of two familial cases and review of the literature.

We present four children from two families with the typical 11q- phenotype resulting from an unbalanced segregation of a parental translocation. In the first family, the father had a 46,XY,t(5;11)(q24;q23.3) constitution. The father of the three other children had a 46,XY,t(11;17)(q23;p13) translocation. Despite associated partial deletion, three of the children had a typical 11q- phenotype. The fourth one, whose pregnancy was terminated in the second trimester, had a hypoplastic left heart but no other considered gross anomalies. A review of 36 previous cases, including 5 due to translocations (4 familial rearrangements, and 1 of unknown origin) is given with emphasis on the relationships between break-points and phenotype. Undescribed manifestations in our patients include agenesis of corpus callosum adactyly and malrotation of the gut.

Inv(12)(q15q24): a nonrandom change associated with myelodysplasia?

A patient with refractory anemia and a paracentric inversion of chromosome 12, inv(12)(q15q24), is described. This is the second reported case with this chromosome anomaly, suggesting that this rearrangement is a rare but nonrandom change associated with myelodysplastic syndromes.

Translocation (2;3)(p21;q26) as the sole anomaly in a case of primary myelofibrosis.

Translocation t(2p;3q) is a rare but recurrent finding in myeloid disorders. We present the first case of primary myelofibrosis with t(2;3)(p21;q26) as the sole chromosomal anomaly. The comparison with the 11 other previously published myeloid-associated t(2p;3q) cases confirms that this nonrandom translocation involves a pluripotent stem cell and is associated with a poor prognosis.

Cytogenetic study of bovine oocytes matured in vitro.

Described in the present paper is a cytogenetic study of bovine oocytes matured in vitro. The cumulus-oocyte complexes (COC), punctured from ovaries recovered in a local slaughterhouse, were classified into 3 groups according to follicular diameter 1 to 4mm, 5 to 8mm and 9 to 13 mm. Metaphases available for observation were classified as metaphase I, haploid and diploid metaphase II. High levels of haploid metaphases II (90.6, 86.9 and 94.4 %) among the 3 groups of follicular sizes indicated successful meiotic resumption during in vitro maturation and suggested that cytoplasmic maturation may be responsible for low developmental rate after IVM, IVF and in vitro development (IVD).

A low rate of trisomy 21 in twin-pregnancies: a cytogenetics retrospective study of 278 cases.

From January 1st 1990 until December 31st 2001, we collected 19686 prenatal diagnosis (on amniocentesis and chorius villus sampling). Five hundred twelve samples (2.6%) concerned 278 twin pregnancies. The most frequent indications were maternal age > or = 35 years (108/278 = 38.8%), medically assisted procreation (34/278 = 12.3%), positive ultrasound (20/278 = 7.2%). Chromosome abnormalities were found in eight twin-pregnancies (2.9%): five with only one fetus affected [47,XX,+ 18; 45,XX,t( 13;14); 47,XYY; 47,XXX; 45,XX, t(13;14)], two with both fetuses showing the same chromosomal abnormality [inv(11)(q21q25); 47,XX,+ 18] and one with only one fetus tested [47,XX,+ 18]. In total, we found eight autosomal abnormalities, four inherited balanced rearrangements (two robertsonian translocations and two paracentric inversions of chromosome 11) and four trisomies 18. We also observed two sex chromosome abnormalities interesting only one of the two fetuses. Surprisingly, we did no detect any Down Syndrome among this population. The frequency of Down Syndrome was significantly (p < 0.05) lower in our population of twin pregnancies (0.0%) as compared to the observed incidence in singleton pregnancies during the same period (163/19162 = 0.9%).

Episphalosomic syndrome : a MCA syndrome ressembling Fanconi anemia, with increased baseline level of chromosome breaks but no hypersensivity to clastogens.

We describe a child with facial dysmorphism (trigonocephaly, epicanthus, upturned nose, small ears), thumb hypoplasia, micropenis, jejunal atresia and moderate mental retardation with dysphasia. Cytogenetic workup revealed high spontaneous level of chromosomal aberrations (without specific pattern and no quadriradial figures) and borderline to absent hypersensitivity to mitomycin C, making a diagnosis of Fanconi anemia unlikely. The child described here shares similarities with a small number of previous reports. We suggest to refer to this entity as episphalosomic syndrome. Episphalosomic syndrome shows some clinical overlap with Fanconi anemia, but lacks its cytogenetic hallmark. The hematological complications of Fanconi anemia have not been reported in this entity.

Submicroscopic terminal deletions and duplications in retarded patients with unclassified malformation syndromes.

Unbalanced submicroscopic subtelomeric chromosomal rearrangements represent a significant cause of unexplained moderate to severe mental retardation with and without phenotypic abnormalities. We investigated 254 patients (102 from Zürich, 152 from Liège) for unbalanced subtelomeric rearrangements by using fluorescence in situ hybridisation with probes mapping to 41 subtelomeric regions. Mental retardation combined with a pattern of dysmorphic features, with or without major malformations, and growth retardation and a normal karyotype by conventional G-banding were the criteria of inclusion. Selection criteria were more restrictive for the Zürich series in terms of clinical and cytogenetic pre-investigation. We found 13 unbalanced rearrangements and two further aberrations, which, following the investigation of other family members, had to be considered as variants without influence on the phenotype. The significant aberrations included three de novo deletions (two of 1pter, one of 5pter), three de novo duplications (8pter, 9pter, Xpter), one de novo deletion 13qter-duplication 4qter, and five familial submicroscopic translocations [(1q;18p), (2q;4p), (2p;7q), (3p;22q), (4q;10q), (12p;22q)], most of them with several unbalanced offspring with deletion-duplication. Although the incidence of abnormal results was higher (10/152) in the Liège versus the Zürich series (3/102), similar selection criteria in Zürich as in Liège would have resulted in an incidence of 7/106 and thus similar figures. In our series, submicroscopic unbalanced rearrangements explain the phenotype in 13/254 study probands. The most important selection criterion seems to be the presence of more than one affected member in a family. An examination of subtelomeric segments should be included in the diagnostic work-up of patients with unexplained mental retardation combined with physical abnormalities, when a careful conventional examination of banded chromosomes has yielded a normal result and a thorough clinical examination does not lead to another classification. The proportion of abnormal findings depends strongly on selection criteria: more stringent selection can eliminate some examinations but necessitates a high workload for experienced clinical geneticists. Once the costs and workload of screening are reduced, less selective approaches might finally be more cost-effective.

Genetic risk in natural and medically assisted procreation.

Current in vitro fertilization techniques (IVF) including intracytoplasmic sperm injection (ICSI), microepididymal sperm aspiration (MESA) or testicular sperm extraction (TESE) clearly prevent any spontaneous choice of ova or spermatozoa. According to the widely admitted concept of gamete selection, pregnancies following IVF, when compared to natural fertilization, could therefore present a higher risk of genetic anomalies. However, no increased fetal or newborn abnormalities are noticed with IVF, except perhaps for sex chromosome aneuploidies. Data from the literature support the view that the uterus is, indeed, the organ where selection mechanisms occur (when they do so), as suggested by Carr in 1971. This selection concerns mainly autosome imbalances; unbalanced conceptuses are aborted. Sex chromosome aneuploidies, apparently, are less prone to natural abortion, but their higher rate of occurrence, as reported in a few series of studies, does not seem to be associated with the IVF procedures.

Loss of the Y chromosome in bone marrow cells: results on 1907 consecutive cases of leukaemia and preleukaemia.

Loss of the Y chromosome with a resulting 45, X0 karyotype is observed in normal bone marrow cells of elderly males but also in haematological malignancies. Whether Y loss in neoplastic cells is related to the process seen in normal ageing or is part of the carcinogenic process is unknown. The present study concerns the cytogenetic data from 1907 consecutive leukaemic or preleukaemic male patients with special regard to the presence or absence of the Y chromosome. Sixty-five patients (3.4%) had a 45, X-Y clone in their bone marrow (BM) cells. Loss of Y was rare below the age of 50 but increased in older patients, reaching 25% of the men over 80. Sixteen patients (0.08%) had more than 90% X0 cells in their BM. A correlation between Y loss and leukaemia could be established in seven cases, three of which were acute myeloid leukaemia M2 subtype where -Y is known to be a secondary event. In three other cases, -Y was part of a complex karyotype. Only one patient exhibited a 45, X0 karyotype, with no other rearrangement, that could be positively correlated with the neoplastic process.

Juvenile rheumatoid arthritis and del(22q11) syndrome: a non-random association.

Del(22q11) is a common microdeletion syndrome with an extremely variable phenotype. Besides classical manifestations, such as velocardiofacial (Shprintzen) or DiGeorge syndromes, del(22q11) syndrome may be associated with unusual but probably causally related anomalies that expand its phenotype and complicate its recognition. We report here three children with the deletion and a chronic, erosive polyarthritis resembling idiopathic cases of juvenile rheumatoid arthritis (JRA). Patient 1, born in 1983, initially presented with developmental delay, facial dysmorphism, velopharyngeal insufficiency, and severe gastro-oesophageal reflux requiring G tube feeding. From the age of 3 years, he developed JRA, which resulted in severe restrictive joint disease, osteopenia, and platyspondyly. Patient 2, born in 1976, had tetralogy of Fallot and peripheral pulmonary artery stenosis. She developed slowly, had mild dysmorphic facial features, an abnormal voice, and borderline intelligence. JRA was diagnosed at the age of 5 years. The disorder followed a subacute course, with relatively mild inflammatory phenomena, but an extremely severe skeletal involvement with major osteopenia, restrictive joint disease (bilateral hip replacement), and almost complete osteolysis of the carpal and tarsal bones with phalangeal synostoses, leading to major motor impairment and confinement to a wheelchair. Patient 3, born in 1990, has VSD, right embryo-toxon, bifid uvula, and facial dysmorphism. She developed JRA at the age of 1 year. She is not mentally retarded but has major speech delay secondary to congenital deafness inherited from her mother. In the three patients, a del(22q11) was shown by FISH analysis. These observations, and five other recently published cases, indicate that a JRA-like syndrome is a component of the del(22q11) spectrum. The deletion may be overlooked in those children with severe, chronic inflammatory disorder.