Down syndrome in two siblings with 47,XY,+21 and 46,XY/46,XY,-21,+t(21q;21q)

Summary This is the first report in the literature of siblings affected with Down syndrome; one sibling had a nondisjunction of chromosome 21 and the other a (21q;21q) translocation.     

Cytogenetic and molecular studies of Down syndrome individuals with leukemia.

There is an increased risk of leukemia in Down syndrome (DS) patients, with estimates ranging from 14 to 30 times the incidence rate observed for chromosomally normal children. Furthermore, one type of leukemia, called "transient leukemia" (TL), occurs almost exclusively in DS infants. The basis of the association between DS and leukemia is unknown, but we and others have hypothesized that it may be influenced by the mechanism of origin of the extra chromosome. Therefore, we initiated a cytogenetic and molecular study of nondisjunction in leukemia DS individuals. To date, we have obtained blood and/or tissue samples from 55 individuals consisting of 17 cases with TL, 7 cases of acute nonlymphocytic leukemia subtype M7 (ANLL-M7, or acute megakaryoblastic leukemia, postulated to be related to TL), and 31 cases of other forms of leukemia. Analysis of these cases suggests differences between DS children with TL and those with other types of leukemia or DS individuals with no history of leukemia. Specifically, the TL and ANLL-M7 cases have a highly significant increase in the frequency of "atypical" constitutional karyotypes (i.e., mosaic trisomies, rings, and/or isochromosomes) and are almost always male. Additionally, genetic mapping studies suggest an increase in the frequency of disomic homozygosity, especially in proximal 21q, in DS individuals with TL and ANLL-M7.     

Two Down syndrome patients with rec(21),dupq,inv(21)(p11;q2109) from a familial pericentric inversion

Aneusomie de recombinaison arose from a familial pericentric inversion of a chromosome 21. Two female patients had a typical Down syndrome; one of them had slight psychomotor retardation. There was partial trisomy 21q2109----qter in these two patients but ZnCu SOD activity was normal.     

Analysis of DNA polymorphisms suggests that most de novo dup(21q) chromosomes in patients with Down syndrome are isochromosomes and not translocations.

Down syndrome is rarely due to a de novo duplication of chromosome 21 [dup(21q)]. To investigate the origin of the dup(21q) and the nature of this chromosome, we used DNA polymorphisms in 10 families with Down syndrome due to de novo dup(21q). The origin of the extra chromosome 21q was maternal in six cases and paternal in four cases. Furthermore, the majority (eight of 10) of dup(21q) chromosomes were isochromosomes i(21q) (four were paternal in origin, and four were maternal in origin); however, in two of 10 families the dup(21q) chromosome appeared to be the result of a Robertsonian translocation t(21q;21q) (maternal in origin in both cases).     

Cytogenetic studies of a family with trisomy 21 mosaicism in two successive generations as the cause of Down's syndrome

Summary A family with trisomy-21 mosaicism in two successive generations and a Down's syndrome child in the third generation is presented. Cytogenetic studies of eight individuals of this family showed a marker chromosome 15ph+ and a heteromorphic chromosome 18 in some members. The standard trisomy 21 in the proband was derived from a trisomy-21 oogonium by secondary nondisjunction in his mother.     

Cytogenetic studies using various clastogens in two patients with Werner syndrome and control individuals

Summary Chromosome studies were performed on peripheral lymphocytes from two patients with Werner syndrome and two healthy control individuals to detect spontaneous and/or mutagen-induced chromosomal instability of this disease. Diepoxybutane, isonicotinic acid hydrazide, 4-nitro-quinoline-1-oxide, and bleomycin were used as standard clastogens. While the spontaneous frequency of chromosomal breakage was much higher in lymphocytes from both patients than in the control cells, the basic rate of sister chromatid exchange (SCE) was found to be in the control range. The sensitivity to clastogens of the patients' cells, however, was not substantially increased as compared with the controls if the degree of multiplication of the spontaneous breakage rate or SCE frequency was taken as the basis for comparison. No indication of a greater inhibition of proliferation by the clastogens in the patients' cells than in normal cells was observed using BrdU-labelled lymphocytes. Thus, the lymphocytes from both patients of the present study lacked essential features of the classical chromosome instability syndromes.     

Siblings with opposite chromosome constitutions,dup(2q)/del(7q) and del(2q)/dup(7q)

Chromosome 7q36 microdeletion syndrome is a rare genomic disorder characterized by underdevelopment of the brain, microcephaly, anomalies of the sex organs, and language problems. Developmental delay, intellectual disability, autistic spectrum disorders, BDMR syndrome, and unusual facial morphology are the key features of the chromosome 2q37 microdeletion syndrome. A genetic screening for two brothers with global developmental delay using high-resolution chromosomal analysis and subtelomeric multiplex ligation-dependent probe amplification revealed subtelomeric rearrangements on the same sites of 2q37.2 and 7q35, with reversed deletion and duplication. Both of them showed dysmorphic facial features, severe disability of physical and intellectual development, and abnormal genitalia with differential abnormalities in their phenotypes. The family did not have abnormal genetic phenotypes. According to the genetic analysis of their parents, adjacent-1 segregation from their mother's was suggested as a mechanism of their gene mutation. By comparing the phenotypes of our patients with previous reports on similar patients, we tried to obtain the information of related genes and their chromosomal locations.     

Sleep problems in individuals with 11q terminal deletion disorder (Jacobsen syndrome)

Characteristics of sleep and sleep problems were investigated in 43 individuals with 11q terminal deletion disorder (Jacobsen syndrome). Data were collected using a sleep questionnaire. Ten individuals (23%) had a sleep problem. Settling problems, frequent night waking and early waking occurred in 2 (4%), 7 (16%) and 2 (6%) individuals, respectively. Twenty-two individuals (54%) had a history of sleep problems. Twenty-five individuals (60%) showed restless sleep and 23 individuals (54%) slept in an unusual position. Apart from frequent coughs, no significant relationships were found between the presence of a sleep problem and other variables, such as age, level of ID, breathing problems, heart defects, constipation, daytime activity and behavioral diagnosis, restless sleep and sleeping in an unusual positions.     

Cytogenetic and clinical studies in five cases of inv dup(15)

Summary Inv dup(15) is a clinically significant bisatellited derivative of chromosome 15. Five unrelated patients with this abnormality are described and compared with ten confirmed and nine suspected cases in the literature. Mental and developmental retardation, hypotonia, behavioral disturbances, seizures, abnormal dermatoglyphics, and mild somatic anomalies were the most consistent findings. The extra chromosomes in our patients were identified with the aid of various techniques, including distamycin A/DAPI banding. A comparison of satellite polymorphisms suggested that the rearrangements frequently arose by meiotic nonsister chromatid exchange and second-division nondisjunction. A maternal origin was indicated in two cases, and parental ages were distinctly elevated.     

A large family with subtelomeric translocation t(18;21)(q23;q22.1) and molecular breakpoint in the Down syndrome critical region

We describe a 17-month-old infant with clinical features of Down syndrome and a normal karyotype by standard chromosomal analysis, her two uncles aged 28 and 30 years, respectively, with reduced intelligence and unusual appearance but not apparent Down syndrome, and a severely retarded 6-year-old girl with dysmorphy and epilepsy from the same family. Cytogenetic studies of patients and normal intervening relatives had been carried out at different institutions with normal results. Fluorescence in situ hybridization using whole chromosome painting and unique-copy probes (cosmids) and high-resolution banding revealed a familial subtelomeric translocation of chromosomes 18 and 21, resulting in partial trisomy 21 in the infant and her two uncles, and partial monosomy 21 in the 6-year-old girl. Cytogenetic breakpoints were located in bands 18q23 and 21q22.1, respectively. The molecular breakpoint on chromosome 21 was located between D21S211 (proximal) and D21S1283 (distal) and thus maps within the Down syndrome critical region. Received: 11 November 1996 / Accepted: 29 April 1997     

Sperm nuclei analysis of a Robertsonian t(14q21q) carrier,by FISH,using three plasmids and two YAC probes

The meiotic segregation of chromosomes 14 and 21 was analysed in 1116 spermatozoa from an oligoasthenospermic carrier of a Robsertsonian translocation t(14q21q), and in 16 392 spermatozoa from a control donor, using two-colour fluorescence in situ hybridisation (FISH). Two YAC probes (cloned in yeast artificial chromosomes) specific for regions on the long arms of these chromosomes were co-hybridised. Of the spermatozoa, 12% were unbalanced, resulting from adjacent segregations. Chromosomes X, Y and 1 were also simultaneously detected in 1335 spermatozoa from the same carrier. Whereas gonosomal disomy rates were not significantly different from those of the control donors, disomy 1 were slightly but significantly increased to 0.7%. The diploidy rate was also slightly increased to approximately 1% in the translocation carrier.     

t(21q21q)/r[t(21q21q)] mosaic in two unrelated patients with mild stigmata of Down's syndrome

Two cases of t(21q21q)/r[t(21q21q)] mosaic in unrelated infants, 17 and 14 months old respectively are reported. The proportion of cells with the ring chromosome was 45% in the former, 80% in the latter. Both cases had mild manifestations of the Down's syndrome. The origin of this unusual mosaicism as well as the significance of the difference in the proportions of the ring chromosome in the two have been discussed.     

Partial monosomy 11q and trisomy 12q: variable expression in two siblings

Clinical and cytogenetical findings are reported and discussed on two siblings with discordant phenotypes despite having both a terminal 11q deletion and a distal 12q duplication resulting from an unbalanced segregation of a balanced translocation t(11:12)(q23:q24.1) mat. The oldest child, a girl, is the index patient. Her clinical features include intrauterine and postnatal growth retardation, fetal distress, mild hypotonia, early feeding difficulties, moderate developmental delay, especially in language acquisition, a velopharyngeal insufficiency with repeated otorhinopharyngeal infections, facial dysmorphism, heart ventricular septal defect, and abnormal hyperactive behaviour with sometimes autistic tendencies. The facial dysmorphic features notably consist of microcephaly, hypertelorism, large palpebral fissures, large eyes with alternant divergent strabismus, long eyelashes, a long and broad nasal bridge, a short "crested" nose with salient tip, a fishmouth with large spaces between teeth and flat palate, retrognathism, large ears and multiple dimples. The second affected child is a boy showing low birthweight, moderate developmental retardation with mainly no active language at 32 months, behaviour abnormalities with an autistic tendency, and no major physical anomalies apart from a slight facial hypotonia with often open mouth, dimples on the shoulders and right cryptorchidism. The authors stress the variable clinical expression of the chromosomal imbalance in this family resulting in low birthweight, developmental delay, abnormal behaviour, but different degrees of physical features and dysmorphism. The possible contribution of each of the two aneusomies to the phenotype is discussed.     

Translocation (14;21)(q11;q22) in a woman with history of abortions and a child with Down's syndrome

A translocation (14;21)(q11;q22) was observed in a woman with history of abortions and in her child with Down's syndrome. This appears to be the first report of such a translocation with no centric fusion between the acrocentric chromosomes leading to a count of 45 chromosomes in the carrier and giving birth to a Down's syndrome child.     

Paracentric inversion inv(11) (q21q23) in the Netherlands

Summary We report the result of investigations from 20 families with 72 carriers of the paracentric inversion inv(11)(q21q23) in the Netherlands. There is no increase in the rate of spontaneous abortions among carriers of the inversion or their partners. Also, so far, there are no children with recombinant chromosomes arising from the inversion. It is doubtful whether prenatal diagnosis would be helpful to carriers of this inversion. The results of the genealogy study and geographical distribution are discussed; it is suggested that all the families have arisen from a single mutation.     

Complex translocation t(9;21)(9;22)(q12p13)(q12q11) in the family of a child with 9p trisomy syndrome

Summary Leukocyte peroxidase activity was estimated in 5 patients with the juvenile form of neuronal ceroid lipofuscinosis (Spielmeyer-Vogt's disease) and in 15 healthy controls. In contradiction to recent reports normal activity of p-phenylene diamine mediated peroxidase was found in the patients. The possible role of contamination of the white cell preparation with hemoglobin is discussed.