Caso Reportado De Tetraploidia En Infante De 5 Años Vivo 1k3w33

pediatria polska 88 (2013) 467–471

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Case report/Kazuistyka

Tetraploidy in the era of molecular karyotyping – What we need to Tetraploidia w erze kariotypowania molekularnego - o czym należy pamiętać Joanna Bothur-Nowacka 1,*, Aleksandra Jezela-Stanek 2, Katarzyna Zaniuk 1, Bożenna Goryluk-Kozakiewicz 2, Małgorzata Krajewska-Walasek 2, Anna Dobrzańska 1 1 2

Department of Neonatology, Pathology and Intensive Care, The Children's Memorial Health Institute, Warsaw, Poland Department of Medical Genetics, The Children's Memorial Health Institute, Warsaw, Poland

article info

abstract

Article history:

Tetraploidy is a condition in which there are four complete sets of chromosomes in

Received: 08.05.2013

a single cell. In humans, this would be 92 pairs of chromosomes per cell. A great majority

Accepted: 11.06.2013

of pregnancies with a tetraploid fetus end in miscarriage, or if the pregnancy goes to full

Available online: 14.06.2013

term, the infant dies shortly after birth. Longer surveillance is rarely described. The only method for confirming tetraploidy is karyotyping, in many cases using classical G-ban-

Keywords: Tetraploidy

ding methods. In this paper we would like to present another living individual with

Newborn Karyotyping

cular karyotyping, with array Comparative Genomic Hybridization (aCGH, arrayCGH).

tetraploidy and to revise the syndrome in the light of its diagnostics in the era of mole© 2013 Polish Pediatric Society. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Introduction Tetraploid is a term used to describe organisms having four instead of two paired (homologous) sets of chromosomes. It is a known genetic aberration in humans, but because of its high intrauterine lethality (it is found in 1–2% of early miscarriages), only several clinical reports of infants diagnosed with tetraploidy are available [1–10]. The clinical consequences of tetraploidy are varied and include limited life expectancy and multiple congenital anomalies (MCA). A reliable diagnosis can be established only by cytogenetic analyses, which allow the visualization of chromosomes for

chromosomal rearrangements, including numerical and structural aberrations. In this paper we report a 1.5-year-old boy with complete tetraploidy and review clinical features described in this aberration so far in order to raise clinicians' awareness of the symptoms, and point to G-banded karyotyping as a firsttier test.

Case presentation The proband is the second child of healthy, non-consanguineous parents. His family history is unremarkable. Prenatal

* Corresponding author at: The Children's Memorial Health Institute, Aleja Dzieci Polskich 20, 04-730 Warsaw, Poland. Tel.: +48 22 815 77 66; fax: +48 22 815 17 85. E-mail addresses: [email protected] (J. Bothur-Nowacka). 0031-3939/$ – see front matter © 2013 Polish Pediatric Society. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved. http://dx.doi.org/10.1016/j.pepo.2013.06.002

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ultrasound revealed no abnormalities. He was born at week 40 of gestation with a weight of 2415 g and scored 5-8-8 points on the Apgar scale. Facial dysmorphism, microphtalmia, skin defects of the scalp, and a loud systolic murmur over the heart were noted at birth. Moreover, he presented with severe breathing difficulties and therefore was referred to the Department of Neonatology and Intensive Care of the Children's Memorial Health Institute in Warsaw. In the physical examination, numerous dysmorphic features were found: long cranium, sparse, fair hair, loss of skin on top of the head (on an area of 2 cm 2 cm), hypoplastic, lowset and rotated ears, long face, high forehead, short palpebral fissures, lack of the right eyeball and small left eyeball, long nose with pressed nasal tip and hypoplastic alae nasi, narrow upper lip, microstomia, short neck (Fig. 1). Moreover, high palate, club foot, long toes and arachnodactyly with long fingernails, abnormal position of the thumbs (Fig. 2), hypoplastic external genitalia (micropenis, small testes in the scrotum) were noted. The boy presented with muscle hypotonia and low spontaneous activity. Echocardiography revealed a significantly and atypically rotated heart, patent ductus arteriosus (PDA), and atrial septal defect (ASD). No abnormalities were noted in abdominal ultrasound, while transfontanellar study revealed small cysts with a diameter of 2–4 mm in the floor of the lateral ventricles and an uneven outline of the plexus choroideus. After obtaining informed consent, peripheral blood samples were taken from the patient. Chromosome analysis at the 550-band level was performed on peripheral blood lymphocytes according to standard procedures using trypsin and giemsa for G-banding. It showed regular tetraploidy with the karyotype 92,XXYY (Fig. 3). This result was then verified in fibroblast analyses, which confirmed this ploidy. Taking into consideration this diagnosis, it was decided to abstain from further cardiologic and ophthalmic tests. The boy was transferred to the care of the Warsaw Hospice for Children (WHD). At 24 days of life the patient was discharged from the hospital in good condition to his home. At present, at the age of one year and 8 months, he still is at home under the care of the WHD. He is profoundly

Fig. 1 – Male patient with regular tetraploidy, facial appearance

Fig. 2 – Male patient with regular tetraploidy

psychomotor retarded, blind, responds only to sound stimuli. His weight is about 10 kg, is teat-fed and partially probe-fed. The dominant problems in the child's care are severe, recurrent respiratory infections.

Discussion Tetraploidy is a condition in which there are four complete sets of chromosomes in a single cell. In humans, this would be 92 sets of chromosomes per cell, i.e., 92,XXXX (in females) or 92,XXYY (in males). The most probable origin of tetraploidy is chromosome duplication in a somatic cell in an early-cleavage-stage embryo, a postzygotic event. Fertilization of a rare diploid ovum by an equally rare unreduced sperm may be possible. Another rare event is fertilization of one egg by three sperms, but this will develop as hydatidiform moles rather than a tetraploid fetus, because of the genomic imprinting effect [11]. A great majority of pregnancies in which the fetus has tetraploidy end in miscarriage (5–6% of genetically abnormal miscarriages), or if the pregnancy goes to full term, usually results in the infant's death shortly after birth. Longer surveillance is rarely described. The patient presented herein is the twelfth live-born case with regular tetraploidy described in the literature so far [1–10]. Six were females and six were males. Except for four cases, all were born at term (38–42 weeks of gestation). Numerous abnormalities were observed in the live-born children (Table I). The most common were: intrauterine hypotrophy and postnatal growth retardation, high and prominent forehead, low-set and dysplastic ears, as well as feet/hand abnormalities. Over 50% of these children had microphthalmia and microcephaly. They presented with a somewhat characteristic facial appearance caused by a beaked nose and micrognathia/retrognathia (Figs. 1 and 2). As presented in Table I, the spectrum of congenital anomalies observed in children with tetraploidy is not

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Fig. 3 – Classical karyotype showing tetraploidy

Table I – Clinical overview of live-born patients with regular tetraploidy Feature

Number of cases (including presented herein)

Head

Microcephaly Prominent forehead Hypertelorism Short palpebral fissures Coloboma Anophthalmia/microphthalmia Cleft lip/palate Micrognathia/retrognathia Abnormal ears

5/9 9/10 6/10 8/11 2/3 6/11 7/9 8/10 8/9

Nervous system

Meningomyelocele Brain malformation (polymicrogyria, hydrocephalus, Arnold–Chiari malformation, Dandy–Walker malformation, hypoplasia of optical and olfactory nerves, cerebellar hypoplasia, cerebral atrophy, hypoplasia of cerebrum, pons, and medulla, hypoplasia of the pituitary gland and thymus)

3/12 6/7

Heart

Patent ductus arteriosus (PDA), patent foramen ovale (PFO), ventricular/atrial septal defect (VSD/ASD), mitral valve prolapse, transposition of the great vessels (TGV), tetralogy of Fallot (TF)

8/11

Genito-urinary tract

Hypoplastic external genitalia/genital ambigiuty Bilateral hypoplasia of the adrenal glands and kidneys

7/10 1/12

Musculo-sceletal system

Positional limb defects/hand abnormalities Arachnodactyly Feet abnormalities

10/11 8/10 4/4

Other

Hypoplastic lungs Enteric cyst located behind the urinary bladder,

2/2 1/12

Birth weight (g)

1728–2650 (mean: 2181)

11

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definitely unique. There are, however, features that are apparently infrequent and uncommon in other chromosomal aberrations. These are: anophtalmia/severe microphtalmia and meningomyelocele. We would like to point out these clinical signs, which, in our opinion, should direct clinicians' attention to diagnostics toward tetraploidy. Cytogenetic analysis is a standard procedure in the evaluation of patients with unexplained developmental delay/intellectual disability (DD/ID) and MCA. Until recently, G-banded karyotyping has been the standard first-tier test for detection of genetic imbalance at all genetic centers, and in many, still is. This method allows the visualization and analysis of chromosomes for chromosomal rearrangements, including numerical (aneuploidy and polyploidy) and structural aberrations (deletion, duplication, inversion). The resolution of this conventional method lies in the range 5– 10 Mb. Therefore, microdeletions and microduplications smaller than 5 Mb will often go undetected. Presently, a commonly ordered clinical genetic test for the patients mentioned above is array Comparative Genomic Hybridization (aCGH, arrayCGH), microarray-based genomic copy-number analysis, known as ‘‘chromosomal microarray’’ (CMA), or ‘‘molecular karyotyping’’ [12]. It offers a much higher diagnostic yield (15–20%) for genetic testing of individuals with unexplained DD/ID or MCA than a G-banded karyotype (3%, excluding Down syndrome and other recognizable chromosomal syndromes) [13]. The level of resolution of aCGH is essentially without limitation, depending only on the size and distance between the arrayed interrogating probes. Molecular karyotyping has, however a few limitations, one of which is detection of regular polyploidy. According to the practice guidelines of the American College of Medical Genetics (ACMG), aCGH should be a firsttier, postnatal test in individuals with multiple anomalies not specific to well-delineated genetic syndromes, individuals with apparently nonsyndromic developmental delay or intellectual disability, and individuals with autism spectrum disorders [13]. This is primarily because of aCGH's high sensitivity for submicroscopic deletions and duplications. Some pathogenic chromosome imbalances are large enough to be detected with conventional chromosome analysis (5– 10 Mb), but many pathogenic rearrangements are at or below the limits of resolution of G-banding chromosome analysis (approximately 5 Mb). There are some limitations of aCGH. These are detection of low-level mosaicism (below 5%-10%), balanced translocation and inversion. Another is detection of polyploidy. Due to the normalization of intensity ratios to the most frequent ratio level, which is considered ‘‘normal’’, array CGH does not provide information such to ploidy. Since a tetraploid clone without further rearrangements has a balanced DNA content, it would appear normal [14–16]. The last limitation is not a rule in all cases, however. Ballif et al. have used a Klinefelter cell line (47,XXY) as a reference control in aCGH tests on products of conception (POCs). Their results suggest that microarrays can potentially detect >80% of all chromosomally abnormal POCs, including some common triploids and other abnormalities of the sex chromosomes [17].

This shows that the analysis of ploidy by genomic microarrays is possible, but it remains a diagnostic challenge. Therefore, we would like to stress in this paper that conventional G-banded karyotyping is better and still necessary when evaluating patients with clinical features of polyploidy. Only this method allows identification of triploidy 69,XXX and tetraploidy 92,XXYY, which is not possible in microarray analyses. An interesting characteristic of tetraploidy is life expectancy. Most reported individuals have died between birth and the age of one year [2–4, 7, 9, 10]. The oldest described non-mosaics tetraploid patient was aged 26 months [8], another female was at least 22-months-old [5]. Our patient presented here is now 18 months old. The prognosis in of survival seems to be an important issue for genetic, especially prenatal, counseling. Obstetricians, neonatologists and clinical geneticists should keep in mind both the unique clinical features of tetraploidy (anophtalmia/microphtalmia and meningomyelocele) and that, in rare cases, complete tetraploidy is compatible with life.

Conclusions Tetraploidy is an extremely rare, usually lethal form of chromosomal aberration. The clinical picture is dominated by intrauterine hypotrophy, profound delay in psychomotor development, microcephaly, and craniofacial defects. Due to the widespread phenotype consequences, the diagnosis must be confirmed, however, by cytogenetic analyses using classical G-banding methods.

Authors' contributions/Wkład autorów JB-N, AJ-S MK-W, and AD performed study design. JB-N, AJ-S and BG-K made data collection, where AJ-S made data interpretation and KZ performed literature search also. MKW and AD verified the final manuscript version.

Conflict of interest/Konflikt interesu None declared.

Financial /Finansowanie None declared.

Ethics/Etyka The work described in this article has been carried out in accordance with The Code of Ethics of the World Medical Association (Declaration of Helsinki) for experiments involving humans; EU Directive 2010/63/EU for animal experiments; Uniform Requirements for manuscripts submitted to Biomedical journals.

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