Phenotypical variation in cousins with the identical partial trisomy 9 (pter-q22.2) and 7 (q35-qter) at 16 and 23 weeks gestation

From the study of numerical and structural chromosomal abnormalities, there is convincing evidence and accumulating information of a direct karyotype to phenotype correlation. Knowledge of phenotypic consequences of a specific chromosomal imbalance is important for genetic counseling and prenatal diagnosis. However, for unbalanced non-Robertsonian translocations a precise karyotype to phenotype correlation is difficult to predict for several reasons: (I) unbalanced non-Robertsonian translocations are rare, (II) the published case reports are often not age-matched, (III) varying breakpoints result in different lengths of the monosomic and trisomic segments and therefore the phenotype will depend on additional genes present or the loss of coding regions, and (IV) the combination of the same trisomy with different monosomies, or vice versa, can result in diverging phenotypes. Therefore, the study of the karyotype to phenotype correlation in affected relatives of the same age and the identical unbalanced translocation provides a good model to investigate phenotypic consequences of a specific genetic imbalance. We report of two second trimester fetuses with the identical major partial trisomy 9 (9pter-9q22.2) and minor partial trisomy 7 (q35-qter) resulting from a familial translocation (7;9)(q35;q22.2)mat. One fetus presented with a Dandy-Walker malformation, polymicrogyria, and mild dysmorphic features, whereas the other fetus showed unilateral cleft lip and palate without cerebral anomalies. Potential mechanisms for this different phenotypic expression of the same unbalanced translocation resulting in partial trisomy 9 and 7 in the two cousins and possible consequences for genetic counseling and prenatal diagnosis are discussed.     

Autosomal recessive congenital cerebellar hypoplasia

We report three sibling pairs with congenital cerebellar hypoplasia. All six children presented in the first years of life with delays in motor and language development. All patients showed cerebellar and/or vermal dysfunction and, on formal psychometric testing, cognitive abilities ranged from normal to moderately retarded. Abnormalities on CT scan ranged from prominent valleculla to an enlarged cisterna magna with hypoplasia of the cerebellar hemispheres and vermis. The pedigrees are consistent with autosomal recessive inheritance.     

3.2 Mb microdeletion in chromosome 7 bands q22.2–q22.3 associated with overgrowth and delayed bone age

We report a patient with mental retardation, epilepsy, overgrowth, delayed bone age, peculiar facial features, corpus callosum hypoplasia, enlarged cisterna magna and right cerebellar hypoplasia. Array-CGH analysis revealed the presence of a de novo 3.2 Mb interstitial deletion of the long arm of chromosome 7 involving bands q22.2–q22.3. The rearrangement includes 15 genes and encompasses a genomic region that represents a site of frequent loss of heterozygosity in myeloid malignancies. Four genes are implicated in the control of cell cycle: SRPK2, MLL5, RINT1 and LHFPL3. Haploinsufficiency of these genes might therefore be associated with overgrowth and could confer susceptibility to cancers or other tumours, so that attention to this possibility would be appropriate during regular medical review. In conclusion, array-CGH analysis should be performed in patients with overgrowth where the known causes have already been excluded, because some still unclassified overgrowth syndromes may be caused by subtle genomic imbalances.     

Neuropathological features in a female fetus with OPHN1 deletion and cerebellar hypoplasia

We report the case of a 33-year-old pregnant woman. The third-trimester ultrasound scan during pregnancy revealed fetal bilateral ventricular dilatation, macrosomia and a transverse diameter of the cerebellum at the 30th centile. A brain MRI scan at 31 weeks of gestation led to a diagnosis of hypoplasia of the cerebellar vermis without hemisphere abnormalities and a non compressive expansion of the cisterna magna. The fetal karyotype was 46,XX. The pregnancy was terminated and array-CGH analysis of the fetus identified a 238 kb de novo deletion on chromosome Xp12, encompassing part of OPHN1 gene. Further studies revealed a completely skewed pattern of X inactivation. OPHN1 is involved in X-linked mental retardation (XLMR) with cerebellar hypoplasia and encodes a Rho-GTPase-activating protein called oligophrenin-1, which is produced throughout the developing mouse brain and in the hippocampus and Purkinje cells of the cerebellum in adult mice. Neuropathological examination of the female fetus revealed cerebellar hypoplasia and the heterotopia of Purkinje cells at multiple sites in the white matter of the cerebellum. This condition mostly affects male fetuses in humans. We report here the first case of a de novo partial deletion of OPHN1, with radiological and neuropathological examination, in a female fetus.     

Trisomy 16pter to 16q12.1 and monosomy 22pter to 22q11.2 resulting from adjacent-2 segregation of a maternal complex chromosome rearrangement

We report on a 16-week-old male fetus with partial trisomy 16 and partial monosomy 22 resulting from 3:3 adjacent-2 segregation of a maternal balanced complex chromosome translocation involving chromosomes 5, 16, and 22. The karyotype of the 29-year-old phenotypically normal mother was 46,XX,t(5;16;22)(q31.3;q12.1;q11.2). The karyotype of the fetus was 46,XY,der(5)t(5;16;22)(q31.3;q12.1;q11.2),+der(16)t(5;16;22)mat,−22. The fetus had multiple congenital anomalies, including bilateral cleft lip and palate. Am. J. Med. Genet. 73:327–329, 1997. © 1997 Wiley-Liss, Inc.     

Analysis of a familial three way translocation involving chromosomes 3q, 6q, and 15q by high resolution banding and fluorescent in situ hybridisation (FISH) shows two different unbalanced karyotypes in sibs.

We report on a familial three way translocation involving chromosomes 3, 6, and 15 identified by prometaphase banding and fluorescence in situ hybridisation (FISH). Two mentally retarded sibs with different phenotypic abnormalities, their phenotypically normal sister and mother, and two fetuses of the phenotypically normal sister were analysed. The terminal regions of chromosomes 3q, 6q, and 15q were involved in a reciprocal translocation, in addition to a paracentric inversion of the derivative chromosome 15. Conventional cytogenetic studies with high resolution GTG banding did not resolve this rearrangement. FISH using whole chromosome paints (WCPs) identified the chromosomal regions involved, except the aberrant region of 3q, which was undetectable with these probes. Investigation of this region with the subtelomeric FISH probe D3S1445/D3S1446 showed a balanced karyotype, 46,XX,t(3;15;6) (q29;q26.1;q26), inv der(15) (q15.1q26.1) in two adult females and one fetus. It was unbalanced in two sibs, showing two different types of unbalanced translocation resulting in partial trisomy 3q in combination with partial monosomy 6q in one patient and partial trisomy 15q with partial monosomy 6q in the other patient and one fetus. These represent apparently new chromosomal phenotypes.     

An unbalanced autosomal translocation (7;9) associated with feminization

A newborn girl presented with generalized mild dysmorphic features. She later developed heart failure and hydrocephalus, and died aged 5 months. Chromosome analysis revealed an unbalanced reciprocal translocation (with partial trisomy for half of the long arm of 7 and partial monosomy for the short arm of chromosome 9) and normal but inappropriate sex chromosomes (XY). The karyotype (46,XY,-9, +der(9),t(7;9)(q31.1;p23)pat) was inferred from her father who was a balanced carrier: 46, XY,(7;9)(q31.1;p23). The evidence of the present case, when considered with that of previous reports, suggests that deletion of genes on the 9p may have caused the feminization and therefore that the 9p region may contain genes which are important in the normal process of testis formation.     

Fetus with two identical reciprocal translocations: description of a rare complication of consanguinity

We report on a 24-week fetus with multiple organ anomalies secondary to biparental inheritance of an apparently balanced t(17;20) reciprocal translocation. The pregnancy was terminated following the discovery by ultrasound of an abnormal heart and micrognathia. At autopsy, the following anomalies were found: Pierre-Robin sequence, hypoplasia of the right ventricle with muscular hypertrophy, and endocardial fibroelastosis, hypoplastic lungs, dysplastic left kidney, bilateral pelvicalyceal dilatation, central nervous system periventricular heterotopias and right sided club foot. Given the endocardial fibroelastosis and cleft palate, Eastman-Bixler syndrome (Facio-cardio-renal) is a possible diagnosis. The parents were first cousins and each had an identical t(17;20)(q21.1;p11.21) translocation. The fetal karyotype was 46,XX,t(17;20)(q21.1;p11.21)mat,t(17;20)(q21.1;p11.21)pat. While there are a few reports of consanguineous families where both the mother and father had the same reciprocal translocation and offspring with unbalanced karyotypes, we were unable to find any reports of a fetus/child with double identical reciprocal translocations. We propose that although the fetus had an apparently balanced karyotype, inheriting only the translocated chromosomes led to the unmasking of a recessive syndrome. It seems most likely that a gene (or genes) was disrupted by the breaks but the parents might also be heterozygous carriers of a recessive gene mutation since the fetus must be homozygous by descent for many loci on both chromosomes 17 and 20 (as well as on other chromosomal segments). It was not possible to totally exclude segmental uniparental disomy as a cause of the anomalies as no recombinations were detected for chromosome 17. However, there is no evidence to suggest that chromosome 17 is imprinted and UPD 20 was excluded thus making an imprinting error unlikely.     

Dandy-Walker variant in Coffin-Siris syndrome

We describe a five-month-old male infant with Coffin-Siris syndrome, the so-called Dandy-Walker variant (hypoplasia of the cerebellar vermis with cystic dilatation of the fourth ventricle, but without enlargement of the posterior fossa), and partial agenesis of the corpus callosum. Dandy-Walker malformation and mega cisterna magna, but not Dandy-Walker variant, have been reported in Coffin-Siris syndrome. The presence of Dandy-Walker variant in the infant we described confirms that the full continuum of the Dandy-Walker complex can occur in Coffin-Siris syndrome. The yet unidentified gene(s) for the syndrome may be related to the development of the hindbrain.     

Partial trisomy 5q and partial monosomy 5q within the same family

The observation of partial trisomy for 5q31-5qter and partial monosomy for the same segment in two offspring within the same family is presented. Their normal mother was a balanced carrier of a reciprocal translocation 46,XX,t(5;10) (q31.3;q26). The trisomic female had craniofacial dysplasia, a short neck, clinodactyly of the 5th fingers, a small umbilical hernia, arhinencephalia, cerebellar hypoplasia, atrial septal defect, an accessory spleen, bifid uterus and vagina, hypoplastic ovaries. Potter syndrome with cystic dysplasia of the left kidney and agenesis of the right, urethral atresia, uterus unicornus with utero-urethral fistula, true hermaphroditism with two ovaries and one testicle were found in her stillborn sister. Analysis of the manifestations of monosomy 5q and trisomy 5q in the same family supports a well known fact that the effects of deletions are more pronounced than those of duplications for the same segments.     

Dandy-Walker(like) malformation, atrio-ventricular septal defect and a similar pattern of minor anomalies in 2 sisters: a new syndrome?

We report on sisters with similar craniofacial anomalies, a brain malformation in the area of the posterior fossa, and a congenital heart defect. The craniofacial findings include macrocephaly, a prominent forehead and occiput, foramina parietalia, hypertelorism, downslanting palpebral fissures, a depressed nasal bridge, narrow palate, and apparently low-set ears. Patient 1 had a Dandy-Walker malformation with communicating hydrocephalus, aplasia of the posterior portion of the cerebellar vermis, and high insertion of the confluent sinus, while in patient 2, a Dandy-Walker variant was found with aplasia of the cerebellar vermis and hypoplasia of the hemispheres, large cisterna magna, high insertion of the confluent sinus, but no hydrocephalus. Both sibs were moderately mentally retarded. The older sister had a complete atrio-ventricular canal and died after unsuccessful heart operation at 3 1/2 years. The younger had a successful operation on a cleft mitral valve and septum primum defect. Chromosomes were normal. The occurrence of a distinct and similar pattern of congenital anomalies in sisters born to healthy parents points toward a "new" syndrome caused by the homozygous state of an autosomal recessive gene.     

Intracytoplasmic sperm injection pregnancy with fetal trisomy 9p resulting from a balanced paternal translocation

Infertile men who carry a chromosomal translocation can be successfully treated with intracytoplasmic sperm injection (ICSI). However, such treatment carries a risk that a pregnancy with an abnormal karyotype will be induced. While in all previously published cases the outcome was favourable, we here report the first instance of a parental reciprocal translocation leading to a chromosomally unbalanced ICSI pregnancy. The fetus, one of a pair of dizygotic twins, was found to have trisomy for the short arm of chromosome 9. The parents opted for selective abortion of the affected twin.      

一例1q部分三体4q部分单体导致Pierre Robin序列征的遗传学分析

目的对1例临床诊断为Pierre Robin序列征的患儿进行细胞及分子遗传学分析,寻找遗传学病因。方法应用外周血染色体核型分析、核苷酸多态性微阵列检测和荧光原位杂交技术,分别对1例表型为下颌小、舌后坠、上呼吸道阻塞、上颚裂开、颈短的患儿及其正常表型的父母进行检测。结果患儿核型为46,XY,der(4)add(4)(q34);母亲核型为46,XX,t(1;4)(q43;q34);父亲核型为46,XY。患儿芯片检测结果为arr[hg19]1q42.2q44(232527958-249202755)×3,4q34.3q35.2(168236901-190880409)×1;父母芯片检测结果正常。母亲荧光原位杂交检测结果为ish t(1;4)(q42;34)。母亲为平衡易位携带者;患儿的4号衍生染色体来源于母亲其中一条结构重排的4号染色体,导致1q42.2q44片段三体、4q34.3q35.2片段单体。结论患儿的1号染色体片段重复及4号染色体片段缺失可能导致其Pierre Robin序列征相关表型。     

A boy with proximal trisomy 15 and a male foetus with distal trisomy 15 due to a familial 13p;15q translocation

A familial 13p;lSq translocation was ascertained through a mentally retarded boy with a proximal trisomy 15 syndrome. His mother, who was a balanced 13p;15q carrier, had in addition a legal abortion after 22 weeks of gestation because of a prenatal diagnosis of distal trisomy 15 in a male foetus. Her mother and two sisters, who were balanced carriers, all had children with either a normal karyotype or a balanced translocation or had had pregnancies resulting in an early spontaneous abortion.     

Trisomy 8 in essential thrombocythemia in leukemic transformation

Partial duplication of the long arm of chromosome 1 has been observed in fetal intracranial teratomas. We sonographically diagnosed a 19-week fetus with sacrococcygeal teratoma, cerebral ventriculomegaly, and cerebellar hypoplasia. Chromosomal analysis of amniocytes showed an unbalanced translocation between chromosomes 1 and 15, resulting in trisomy 1q21-->1 qter. Duplication or over expression at more than one locus on the long arm of chromosome 1 may be required for the development of an extra-gonadal teratoma.     

Fetal phenotype in a case of partial trisomy 21 and partial monosomy 22 detected prenatally.

Prenatal diagnosis was performed in a woman whose previous pregnancy resulted in a girl with probable Down syndrome who died soon after delivery. The mother was found to be a carrier of a reciprocal balanced translocation between chromosomes 21 and 22, and the fetus was found to have an unbalanced translocation involving chromosomes 21 and 22: 46,XX, -22, +t(21;22)(q22;q11)(21 pter leads to 21q22::22q11 leads to 22qter). Despite partial monosomy for the proximal segment of 22 and trisomy for proximal 21, the fetus did not have gross external abnormalities, but several internal malformations were found. To our knowledge, this is the first time that this unbalanced karyotype has been described.     

Supernumerary chromosome inherited from a maternal balanced translocation leading to pure trisomy 9p

We describe a child with a supernumerary chromosome defined as der(9)t(9;22) (q12;p11), resulting in trisomy 9p and trisomy 22p. The mother carried the balanced translocation. In G- and C-banding the derivative chromosome 9 appeared to be dicentric and to contain 22q material. Using in situ hybridization we defined the exact breakpoints of the translocation and ruled out the possibility of a centric fission in the mother's chromosomes.     

Tertiary trisomy due to a reciprocal translocation of chromosomes 5 and 21 in a four-generation family

Tertiary trisomy, or double trisomy, is a rare occurrence. We present two individuals with a previously unreported tertiary trisomy for chromosomes 5p and 21q in an eight-generation pedigree. Their phenotypes are compared with other partial trisomies of either 5p or 21q from the literature. The propositus was diagnosed with trisomy 21 at 2 years of age after a karyotype study for short stature and developmental delay. His phenotype was described as atypical for Down syndrome. He presented at 9 years of age because of pervasive behavioral problems and obesity. He was brachycephalic with a flattened nasal bridge, but he lacked other characteristics of trisomy 21. Because of lack of phenotypic evidence of Down syndrome, a repeat karyotype was obtained and showed 47,XY, +der(21)t(5;21)(p15.1; q22.1), incorporating partial trisomies of both chromosomes 5 and 21. Mother had a balanced translocation, 46, XX,t(5;21)(p15.1; q22.1); 8 other relatives were examined. The translocation originated from the maternal great-grandmother, but only the propositus and his mentally retarded aunt had a similar phenotye and the derivative chromosome. Fluorescence in situ hybridization showed absence of band 21q22.2 in the derivative chromosome of the propositus and his aunt, indicating that neither had trisomy for the Down syndrome critical region. These cases represent a unique double partial trisomy of chromosome arms 5p and 21q that occurred because of 3:1 malsegregation of a reciprocal translocation. These cases further demonstrate that phenotypic discordance with cytogenetic results dictate further investigation using advanced cytogenetic hybridization.