Maternal uniparental disomy for chromosome 22 in a child with generalized mosaicism for trisomy 22

Trisomy 22 Mosaicism from Prenatal to Postnatal Findings: A Case Series and Systematic Review of the Literature

BACKGROUND

Among aneuploidies compatible with life, trisomy 22 mosaicism is extremely rare, and only about 25 postnatal and 18 prenatal cases have been described in the literature so far. The condition is mainly characterized by facial and body asymmetry, cardiac heart defects, facial dysmorphisms, growth failure, delayed puberty, and variable degrees of neurodevelopmental delay.

PROBLEM

The scattered information regarding the condition and the dearth of data on its natural history and developmental outcomes restrict genetic counseling, particularly in prenatal settings. Moreover, a prompt diagnosis is frequently delayed by the negative selection of trisomic cells in blood, with mosaicism percentage varying among tissues, which often entails the need for further testing. Purpose/topic: The aim of our work is to provide assistance in prenatal and postnatal genetic counseling by systematically delineating the current knowledge of the condition. This entails defining the prenatal and postnatal characteristics of the condition and presenting novel data from three cases, both prenatally and postnatally. Additionally, we report the developmental outcomes observed in two new patients.

Mosaic trisomy 22 at amniocentesis: Prenatal diagnosis and literature review

OBJECTIVE

We present prenatal diagnosis of mosaic trisomy 22 at amniocentesis in a pregnancy with facial cleft, oligohydramnios and intrauterine growth restriction (IUGR), and we review the literature.

CASE REPORT

A 37-year-old woman underwent amniocentesis at 19 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 47,XX,+22[9]/46,XX[9]. Array comparative genomic hybridization (aCGH) analysis on uncultured amniocytes showed a result of arr(22) × 3 [0.8]. Prenatal ultrasound revealed fetal median facial cleft, oligohydramnios and IUGR. Repeat amniocentesis at 22 weeks of gestation using uncultured amniocytes revealed an aCGH result of arr 22q11.1q13.33 (17,397,498-51,178,264) × 2.8 compatible with 80% mosaicism for trisomy 22, and a fluorescence in situ hybridization (FISH) result of mosaic trisomy 22 with trisomy 22 in 54/100 interphase cells. The cultured amniocytes at repeat amniocentesis had a karyotype of 47,XX,+22[12]/46,XX[8]. The parental karyotypes were normal. Polymorphic DNA marker analysis confirmed a maternal origin of the extra chromosome 22. The pregnancy was terminated, and a 256-g female fetus was delivered with facial dysmorphism and median facial cleft. Cytogenetic analysis of the skin fibroblasts revealed a karyotype of 47,XX,+22[33]/46,XX[7].

CONCLUSION

Fetuses with high level mosaicism for trisomy 22 at amniocentesis may present IUGR, facial cleft and oligohydramnios on prenatal ultrasound.

Mosaic trisomy 22 in a 4-year-old boy with congenital heart disease and general hypotrophy: A case report

BACKGROUND

Trisomy 22 mosaicism is a rare autosomal anomaly with survival compatibility. Recognition of the complete trisomy 22 which is incompatible with life from the mosaic form is critical for genetic counseling. Affected mosaic cases have prevalent clinical presentations such as webbed neck, developmental delay, abnormal ears, cardiac disorders, and microcephaly. Phenotype of these patients is milder than full chromosomal aneuploidy, and the severity of the phenotype depends on the count of trisomic cells. We describe a 4-year-old boy with mosaic trisomy 22 from healthy parents and no family history of any genetic disorders in the pedigree.

METHOD AND RESULTS

The patient had determined dysmorphic clinical features including facial asymmetry, cleft palate, gastroenteritis, hydronephrosis, developmental delay, genital anomalies, dysplastic toenails, flattened nasal bridge, congenital heart defect, hearing loss, cryptorchidism, and hypotonic muscle. He is the first reported with hypothyroidism and larynx wall thickness in worldwide and the first with atrial septal defect (ASD) from Iran. Chromosomal analyses using G-banding indicated a de novo Mos 47,XY,+22(6)/46,XY(44) karyotype with no other chromosomal structural changes.

CONCLUSIONS

Our observations confirm the importance of cytogenetic analyses for determining the cause of congenital anomalies and provide a useful genetic counseling. In addition, due to the fact that some of mosaic trisomy 22 features are unavoidable such as CHD and general hypotrophy, we suggest including echocardiography test for early diagnosis during the clinical assessment.

Recurrent Trisomies: Chance or Inherited Predisposition?

Two patients experiencing recurring trisomic pregnancies involving a different chromosome each time are presented. Mechanisms to explain recurrent trisomies include a gene or genes predisposing to nondisjunction in general or to nondisjunction of the acrocentric chromosomes, maternal age effects, and germ-line mosaicism. Genetic counseling is complicated by the lack of a clear explanation for the recurrences, difficulty in quoting a specific recurrence risk, concern regarding the risk for uniparental disomy, and the frustration, grief and guilt reactions of the patients.

Infantile neuroaxonal dystrophy caused by uniparental disomy

Infantile neuroaxonal dystrophy (INAD) is a rare autosomal recessive neurodegenerative disorder caused by mutations in the phospholipase A2 group 6 (Pla2G6) gene. Affected individuals usually present between the ages of 6 months and 2 years with rapid cognitive and motor regression and axial hypotonia. Gait disturbance, limb spasticity, cerebellar signs, and optic atrophy are other common features associated with INAD. Although magnetic resonance imaging (MRI) can sometimes contribute towards the diagnosis, the confirmation of INAD is by Pla2G6 gene analysis. In this case report, we describe the first individual (female) with INAD due to a combination of uniparental heterodisomy and isodisomy; we discuss the possible underlying mechanism and highlight the importance of parental carrier testing in accurately predicting the recurrence risk in these families. We also confirm the recent report of hypertrophy of the clava (also known as the 'gracile tubercle') as a useful MRI sign in INAD.

Complex cardiac defect, bowing of lower limbs and multiple anomalies in trisomy 22. Ultrasound, post-mortem CT findings with necropsy confirmation

Trisomy 22 is commonly associated with severe intrauterine growth retardation and congenital anomalies. The sonographic identification of a complex cardiac defect and bowing of the long bones associated with multiple structural anomalies add new clinical informations to our knowledge about the prenatal phenotype of trisomy 22. These findings have not been reported previously and are of critical importance as sonographic signs of trisomy 22 may overlap that of trisomy 13-18 and will help clinicians in indicating fetal karyotyping. Prenatal diagnosis of trisomy 22 is essential as trisomy 22 is a lethal condition.

Prenatal diagnosis and postnatal follow-up of a child with mosaic trisomy 22 with several levels of mosaicism in different tissues

We report on the case of a patient with mosaic trisomy 22, who was diagnosed prenatally by amniocentesis during the 16(th) week of pregnancy. In the foetus, three trisomic clones were found out of the nine that were analyzed (the other six clones had a 46,XY karyotype). Cytogenetic analysis of cord blood during the 20(th) week of pregnancy showed a normal male karyotype; however, a placental biopsy that was performed at the same time showed 100% and 95% trisomic cells in the chromosomal analysis of direct and long-term cultures, respectively. A follow-up ultrasonographic examination excluded major congenital malformations and the abdominal and cranial circumferences were normal until the 24(th) week of pregnancy. At this point, a deflection of the growth curve occurred and the values were persistently below the 3(rd) centile until birth. After birth, karyotypic and fluorescent in situ hybridisation analyses performed on the fibroblasts of the neonate showed that 3-4% of the cell lines were trisomic, and studies using microsatellite markers showed normal allelic segregation, which excluded uniparental disomy. The period of postnatal follow-up was characterised by a significant growth deficit (height and head circumference were less than the 3(rd) centile) and by mental retardation. The present case is compatible with other earlier reports that showed that the levels of trisomy 22 are tissue-specific and are of little help in establishing the prognosis of the chromosomal abnormality.

Ocular manifestations of mosaic trisomy 22: A case report and review of the literature

Mosaic trisomy 22 is rare, but can be compatible with prolonged life. Patients with mosaic trisomy 22 usually present with intrauterine growth retardation, mental retardation, failure to thrive, and craniofacial asymmetry. We report the case of a five-year-old boy who had a birth weight of 3.8 kg and normal developmental milestones. He presented with unilateral ocular manifestations of ptosis, double elevator palsy, high myopia, and choroidal coloboma involving the macula. Cytogenetic evaluation showed a low level of trisomy 22 in peripheral blood lymphocytes (1 in 100) and in cultured fibroblasts from a conjunctival biopsy of the affected eye (1 in 60). Our case demonstrates the value of chromosomal analysis of the tissues involved rather than just karyotyping of the blood lymphocytes to detect mosaicism in patients with localised and unilateral congenital malformations.

Sex-specific chromosome instability in early human development

The predominance of females segregating chromosome aberrations to their offspring has been explained mostly by selection disadvantage of unbalanced products of spermatogenesis. However, analysis of data from the literature supports the idea that somatic cells of early female embryos are similar to female germ cells in that they are prone to malsegregation. The goal of this study was to compare the sex ratio (male to female ratio) of carriers of presumably mitotic-occurring chromosome abnormalities to identify any sex biases. In examining the literature, we found a female prevalence in cases of mosaicism associated with uniparental disomy (UPD) (26 male individuals/conceptions and 45 female individuals/conceptions, sex ratio is 0.58, significantly different from 1.06 in newborn population, P = 0.0292). This predominance was highest at gestational age <16 week (8 male and 22 female conceptuses, sex ratio is 0.36, significantly different from expected figure of 1.28, P = 0.0025), which diminished at later stages of fetal development indicating potential correction of trisomies predominantly in females. There is a threefold prevalence of 46,XX/45,X mosaics over 46,XY/45,X mosaics in prenatally diagnosed cases, which also suggests a gender-specific postzygotic chromosome loss. The male prevalence in Prader-Willi syndrome with maternal UPD of chromosome 15 also can be explained by sex-specific trisomy correction, with predominant loss of a maternal chromosome causing biparental inheritance and therefore, complete correction of trisomy in females (without UPD). Finally, there is a female predominance in carriers of chromosome rearrangement with pericentromere break (mosaicism for Robertsonian translocation/isochromosome, centric fission, nonacrocentric isochromosome, and whole arm rearrangement), in both prenatal (21 males and 36 females, sex ratio is 0.58, P < 0.0184) and postnatal ill-defined cases (14 males and 35 females, sex ratio is 0.40, P = 0.001). Thus, the findings presented in this paper suggest that, in addition to reduction in male fertility, and to probable selection against abnormal cell line(s), there are two mechanisms that contribute to female preponderance among carriers of mosaicism: sex-specific chromosome loss and sex-specific centromere instability. The data obtained suggest that females may have gonadal mosaicism for aneuploidies and structural rearrangements more often than males. This may lead to the maternal origin bias in offspring with trisomies or structural rearrangements.

Uniparental disomy (UPD) other than 15: Phenotypes and bibliography updated

Uniparental disomy (UPD) describes the inheritance of a pair of chromosomes from only one parent. The concept was introduced in Medical Genetics by Engel (1980); Am J Med Genet 6:137-143. Aside UPD 15, which is the most frequent one, up to now (February 2005) 197 cases with whole chromosome maternal UPD other than 15 (124 X heterodisomy, 59 X isodisomy, and 14 cases without information of the mode of UPD) and 68 cases with whole chromosome paternal UPD other than 15 (13 X heterdisomy, 53 X isodisomy, and 2 cases without information of the mode of UPD) have been reported. In this review we discuss briefly the problems associated with UPD and provide a comprehensive clinical summary with a bibliography for each UPD other than 15 as a guide for genetic counseling.

Complications of pregnancy and child development after cessation of treatment with 6-mercaptopurine for inflammatory bowel disease

PURPOSE

6-Mercaptopurine (6-MP) has proven efficacy in the therapy of inflammatory bowel disease. Its teratogenicity is demonstrated in animal studies when used at very high doses, whereas human data suggest that 6-MP at maintenance doses is safe. We report the outcome of 72 pregnancies in patients with inflammatory bowel disease who were previously treated with 6-MP with three different doses of 50, 75, and 100 mg/d, for a median duration of 18 months, along with long-term follow-up of the children.

METHODS

We have compared the outcome of pregnancies and development of the offspring in the following two groups: group 1, patients with inflammatory bowel disease who conceived 6 months to 22 years after stopping 6-MP (median 72 months); and group 2, patients with inflammatory bowel disease who never received 6-MP prior to conception. All pregnancies were evaluated in terms of outcome: live full-term birth, premature delivery, stillbirth, spontaneous abortion, ectopic pregnancy, and therapeutic dilatation and curettage. Data on children were obtained regarding birth weight, congenital anomalies, and development.

RESULTS

Group 1 included 72 pregnancies carried by 29 women. There were 51 live births (4 premature), 16 spontaneous abortions, 1 stillbirth, 2 therapeutic abortions due to abnormal amniocentesis, and 2 ectopic pregnancies. The total incidence of fetal loss was 29.2%. In group 2, 75 women had 140 pregnancies resulting in 120 live births (8 premature), 18 spontaneous abortions, and 2 stillbirths. There were no cases of ectopic pregnancies or abnormal amniocentesis. The total incidence of fetal loss was 14.3%. There was no increase in the incidence of developmental defects when the mothers had been treated with 6-MP prior to pregnancy.

CONCLUSIONS

The incidence of fetal loss is higher in women with inflammatory bowel disease who had been previously treated with 6-MP compared with those who had not. Whether this was related to the older age at conception in 6-MP group, longer duration of disease, initially more severe disease, or use of 6-MP we cannot tell.

Language skills in children with velocardiofacial syndrome (deletion 22q11.2)

OBJECTIVE

To further define the language profile of children with velocardiofacial syndrome (VCFS) and explore the influence of parental origin of the deletion on language.

STUDY DESIGN

Children and adolescents with VCFS (n = 27) were group-matched for sex, age, and IQ with 27 children and adolescents with idiopathic developmental delay. Fifty-four typically developing control subjects were also included in the analyses investigating word association abilities.

RESULTS

Children with VCFS had significantly lower receptive than expressive language skills, a unique finding when compared with IQ-matched control subjects. However, no significant differences in word association were detected. Children with a deletion of paternal origin score significantly higher on receptive language when compared with children with a deletion of maternal origin.

CONCLUSIONS

The Clinical Evaluation of Language Fundamentals-III results suggest that children with VCFS show more severe deficits in receptive than expressive language abilities. Language skills of children with VCFS could be influenced by parental origin of the deletion and thus related to neuroanatomic alterations at the deletion site.

No evidence of uniparental disomy 2, 6, 14, 16, 20, and 22 as a major cause of intrauterine growth retardation

Intrauterine growth retardation (IUGR) is defined as length and/or weight below the 10th percentile. Etiology and, consequently, long-term outcome are extremely heterogeneous with chromosomal abnormalities found in up to 7%. Recently, uniparental disomy (UPD), i.e. the inheritance of both homologues of one pair of chromosomes from only one parent, was found in an increasing number of children with IUGR. Particularly, UPD of chromosome 7 was found in up to 10% of patients with IUGR and/or a phenotype of primordial growth retardation or Silver-Russell syndrome (SRS), but also UPD of chromosomes 2, 6, 14, 16, 20, and 22 was reported in single cases with IUGR. To evaluate impact and relevance of UPD in children with IUGR we investigated 23 sporadic cases with IUGR subsequently diagnosed as primordial growth retardation (n = 13) or SRS (n = 10) by molecular methods for UPD of chromosomes 2, 6, 14, 16, 20, and 22. No instance of UPD was found. Inheritance of all chromosomes investigated was biparental in all cases. Therefore, we conclude that UPD of these chromosomes is not a major cause of IUGR.

Severe intra-uterine growth retardation in a patient with maternal uniparental disomy 22 and a 22-trisomic placenta

We report on a maternal uniparental disomy of chromosome 22 in a patient with severe intra-uterine growth retardation. Karyotyping of a placental tissue revealed non-mosaic trisomy 22, whereas lymphocyte chromosomes from the newborn were normal 46,XY. Microsatellite analysis using DNA extracted from white blood cells showed maternal uniparental heterodisomy for chromosome 22. Thus, the conceptus started as maternal trisomy due to meiotic non-disjunction, and trisomy rescue occurred subsequently through loss of the paternal homologue resulting in maternal uniparental disomy. Normal phenotypes in previous reports have suggested that maternal UPD 22 has no impact on the phenotype. Thus, growth retardation in this patient was probably caused by dysfunction of the trisomic placenta.

Growth effects of uniparental disomies and the conflict theory of genomic imprinting

While numerous theories have been proposed for the evolution of genomic imprinting, few have been tested. The conflict theory proposes that imprinting is an intra-individual manifestation of classical parent-offspring conflict. This theory is unique in predicting that imprinted genes expressed from the paternally derived genome should be enhancers of pre- and post-natal growth, while those expressed from the maternally derived genome should be growth suppressors. We examine this prediction by reviewing the literature on growth of human and mouse progeny that have inherited both copies (or part thereof) of a particular chromosome from only one parent. Perhaps surprisingly, we find that much of the data do not support the hypothesis.