Prenatal Diagnosis by FISH of a 22Ql 1 Deletion in Two Families J Med Genet: First Published As 10.1136/Jmg.35.2.165 on 1 February 1998

I Med Genet 1998;35:165-168 165

Prenatal diagnosis by FISH of a 22ql 1 deletion in two families J Med Genet: first published as 10.1136/jmg.35.2.165 on 1 February 1998. Downloaded from

Marie-France Portnoi, Nicole Joye, Marie Gonzales, Suzanne Demczuk, Laurent Fermont, Gilles Gaillard, Guy Bercau, Genevieve Morlier, Jean-Louis Taillemite

Abstract balanced translocation t(I 1;22)(q23;ql 1) was We report on prenatal diagnosis by FISH shown in the father's karyotype; in the second of a sporadic 22qll deletion associated case trisomy X was associated with a 22ql 1 with DiGeorge syndrome (DGS) in two deletion in the fetus. fetuses after an obstetric ultrasonographic examination detected cardiac anomalies, Materials and methods an interrupted aortic arch in case 1 and KARYOTYPING AND FISH tetralogy of Fallot in case 2. The parents Fetal blood samples were obtained for karyo- decided to terminate the pregnancies. At type analysis and FISH. Cells were harvested necropsy, fetal examination showed char- from cultures of phytohaemagglutinin stimu- acteristic facial dysmorphism associated lated lymphocytes and spread onto slides for with congenital malformations, confirm- the production of G banded or R banded chro- ing full DGS in both fetuses. In addition to mosomes. the 22ql 1 deletion, trisomy X was found in FISH of metaphase chromosomes using dig- the second fetus and a reciprocal balanced oxigenin labelled cosmid probes D22S75 translocation t(l 1 ;22) (q23;ql 1) was found (N25, ONCOR) from the DGS chromosome in the clinically normal father of case 1. region was carried out basically according to These findings highlight the importance Pinkel et al.' This probe was premixed with a of performing traditional cytogenetic control cosmid (D22S39) in 22q13.3 facilitat- analysis and FISH in pregnancies with a ing chromosome identification. high risk of a deletion. Service d'Embryologie having Pathologique et de (7Med Genet 1998;35:165-168) Case reports Cytogenetique, Hopital CASE 1 Saint-Antoine, 75012 Keywords: DiGeorge syndrome; chromosome 22ql1; FISH; microdeletion A 31 year old, nulliparous woman, who had Paris, France had a previous miscarriage at 8 weeks of gesta- M-F PortnoY N Joye tion, was seen for fetal echocardiography at 23 M Gonzales DiGeorge syndrome (DGS), an aetiologically weeks of gestation after an obstetric ultrasono- http://jmg.bmj.com/ G Morlier heterogeneous developmental field defect of graphic examination detected cardiac anoma- J-L Taillemite the third and fourth pharyngeal pouches, is lies and absence of the thymic shadow. Fetal characterised by hypoplasia or aplasia of the echocardiography showed an interrupted aor- Cytogenetics, Prenatal tic arch (IAA) associated with a membranous Diagnosis, Montreal thymus and parathyroid glands, a conotruncal Children's Hospital, heart defect, and varying craniofacial ventricular septal defect. The possibility of Montreal, Quebec, dysmorphism.' DGS is frequently associated DGS was discussed because of its strong

Canada with a chromosome 22 abnormality. Unbal- association with IAA and absence of the on September 26, 2021 by guest. Protected copyright. S Demczuk anced translocations which result in mono- thymus. A fetal blood sample was obtained for somy of 22pter-22ql 1 and interstitial deletions karyotype determination. A 46,XX karyotype Unite d'Explorations with a 22ql 1 deletion detected by FISH was Cardiologiques, have mapped the DGS region to 22ql 1.2.2 3 Institut de Molecular studies using probes for various found, consistent with the DG phenotype and Puericulture de Paris, loci in the 22ql 1 region have detected sub- provided a prenatal diagnosis of DGS (fig 1). 75014 Paris, France microscopic deletions in more than 90% The serum calcium level was determined and L Fermont of DGS cases without visible cytogenetic showed hypocalcaemia (66 mg/l, normal fetal Service de Gynecologie abnormalities.4 6 et Obstetrique, H6pital Deletions within 22q1 1 are associated with a Saint-Antoine, 75012 wide variety of birth defects embraced by the Paris, France acronym CATCH 22,7 including Sprintzen G Gaillard syndrome (velocardiofacial syndrome), Service de Gynecologie conotruncal congenital heart disease, and DGS et Obstetrique, H6pital at the more severe end ofthe clinical spectrum. Notre-Dame de This haploinsufficiency of 22ql 1 is a relatively Bon-Secours, 75014 frequent cause of birth defect (1/5000 live Paris, France births).8 Fluorescence in situ hybridisation G Bercau (FISH) using unique sequence DNA probes is Correspondence to: an efficient, quick, and direct method for Dr Portnoi. detection of 22q 1 microdeletions. We report on prenatal diagnosis by FISH of Received 8 April 1997 a 22ql 1 deletion associated with DGS in two Figure 1 Partial metaphase spread showing lack ofsignal Revised version accepted for on one ofthe chromosomes 22. The deleted chromosome 22 publication 30 September families. Both of these cases are sporadic. with distal q arm marker present, but without DiGeorge 1997 Moreover, in the first case, a reciprocal probe signal is indicated by an arrowhead. 166 Portnoi, j7oyi, Gonzales, et al J Med Genet: first published as 10.1136/jmg.35.2.165 on 1 February 1998. Downloaded from

Figure 4 Partial metaphase spread of thefather of case 1 after FISH showing a fluorescent signal on both chromosome 22 homologues at 22q11.2 with probe D22S75 (ONCOR) and at 11q23 on der(l 1) and on normal chromosome 22 with probe D22S39.

levels 90.2 + 8 mg/i). T cell subpopulation .... studies were not performed. The parents were informed about the risks and decided to terminate the pregnancy. At necropsy, fetal examination showed facial dysmorphism with hypertelorism, a square nasal tip, a small, recessed chin, and a small hypoplastic thymus (fig 2). Cardiac examin- Figure 2 Fetus 1. ation confirmed the ultrasonographic findings. The aortic arch ended after the left common carotid artery, consistent with type B interrup- tion, and was associated with a ventricular sep- A tal defect. Neither parent had any evidence of a 22ql 1 deletion by FISH. The mother had normal chromosomes and the father was found to have a balanced reciprocal translocation involving chromosome 22, t(l 1;22)(q23;ql 1).

CASE 2 http://jmg.bmj.com/ Fetal blood was obtained for karyotype analysis from a fetus whose mother and father were 27 and 40 years of age, respectively. Prenatal ultrasound examination at 23 weeks showed tetralogy of Fallot (TF). The fetus was found to have a 47,XXX karyotype and a 22qll deletion detected by FISH. Neither the serum calcium level nor the on September 26, 2021 by guest. Protected copyright. lymphocyte population was evaluated in this case. The TF associated with a 47,XXX karyotype and a 22ql 1 deletion had obvious implications for genetic counselling and risk assessment. Following counselling the pregnancy was terminated. At necropsy, the fetus had facial dysmorphic features including a broad nose, downward slanting palpebral fissures with hypertelorism, a small mouth, microstomia, micrognathia, rounded, posteriorly rotated ears with absent ear lobes, and facial hypertrichosis (fig 3). TF was associated with a complete absence of the thymus, vertebral anomalies, and a left talipes equinovarus deformity. The parental karyotypes were both normal. Deletion 22q1 1 was excluded by FISH.

Discussion Very few data are available concerning the prognosis for fetuses diagnosed prenatally as Fr having a 22ql 1 deletion. To the best of our Figure 3 Fetus 2. knowledge only three cases of prenatally Prenatal diagnosis by FISH of a 22ql1 deletion 167

diagnosed DGS with a 22ql 1 deletion have patients with DGS who have survived infancy been published. have been mildly to moderately retarded.' Van Hemel et al' described a familial case The presence of a deletion associated with J Med Genet: first published as 10.1136/jmg.35.2.165 on 1 February 1998. Downloaded from illustrating the variable clinical expression of conotruncal heart disease is an important point the chromosome 22ql 1 deletion. A 22ql 1 which has obvious implications for genetic deletion was found in a child who died two counselling. In both of our cases, necropsy weeks after birth with symptoms of full DGS confirmed that the fetuses were severely and truncus arteriosus. This deletion was affected and had multiple congenital anoma- detected in the physically normal father who lies. This study, the first to our knowledge that had mild learning disabilities and a tendency to describes fetal examination of DGS with a depression, as well as in a subsequent preg- 22ql 1 deletion, has shown that facial dysmor- nancy. Ultrasound studies did not show cardiac phism is present and recognisable in the fetus or other anomalies in the latter fetus. At birth and is very similar to that of the newborn. the boy developed hypocalcaemia and had a Furthermore, in our report, karyotype moderate T cell deficit. Echocardiography analysis showed a second chromosomal showed a right sided aortic arch without abnormality. In the first case, the father was intracardiac anomalies. found to have a balanced translocation Puder et al" reported a case of prenatally t(1 1;22)(q23;ql 1). FISH analysis showed diagnosed IAA, which led to the detection of D22S75 to be present on the derivative 22 segmental monosomy of chromosome 22qll translocation chromosome and to be located by FISH in the fetus and in his mother, who centromeric to the translocation breakpoint in had a small ventricular septal defect. 22ql1 (fig 4). The presence of a 22ql 1 The first case of prenatal detection of a fetus deletion in the offspring oft(l 1;22) carriers has with an interrupted aortic arch and a 22qll not been reported previously. An attractive deletion, in the absence of a family history, was hypothesis is that this recurrent translocation reported by Davidson et al. 12 The mother was in the father may have played a role in the also found to carry the deletion; she had no existence ofthe deletion in the fetus. Structural cardiac abnormality but was mildly retarded. characteristics of the DNA in the 22ql 1 The pregnancy continued and the prenatal region, especially the presence of low copy diagnosis was helpful for planning postnatal repeat elements, would favour interstitial dele- care. In this family and in others, the deletion tion with more or less precise breakpoint was transmitted from the mother to her more sites.'6 17 However, the role of chance cannot be severely affected child. The range of pheno- excluded. Published data have shown a higher types associated with the 22ql 1 deletion com- frequency of deletions of maternal origin plicates genetic counselling. Moreover, so far (70%).8 In the present case, determination of there has been no experience with the progeny the parental origin of the deleted chromosome of severely affected subjects who nowadays 22 in the fetus was attempted, but was not survive after heart surgery. informative with the polymorphic marker used. http://jmg.bmj.com/ Both ofour cases were referred for cordocen- Further endeavours to obtain other polymor- tesis and fetal blood karyotype analysis in the phic markers mapping to the DGS deleted 23rd week of pregnancy because of detection region and to continue the investigation into by ultrasound examination of a cardiac this family are in progress. anomaly, an IAA associated with thymic aplasia When neither parent has a deletion, it is in the first case and TF in the second. expected that there will be a low risk of having

unusual cardiovas- on September 26, 2021 by guest. Protected copyright. IAA, truncus arteriosus, a further child with a 22ql 1 deletion since cular lesions, and TF are congenital conotrun- gonadal mosaicism cannot be ruled out. In this cal heart diseases commonly found in DGS." diagno- of recent molecular studies in family, an early first trimester prenatal The results sis is relevant because of the risk of inheriting patients with TF, including isolated TF and in the syndromic cases, suggest that isolated TF is not an unbalanced translocation derivative associated with a 22ql 1 deletion, while offspring. hemizygosity for 22ql 1 is present in patients In the second case a triple X karyotype was with TF associated with additional cardiovas- found and the association of triple X with DGS cular or non-cardiac anomalies.'4 '5 Therefore, has never previously been reported either. detection of these cardiac diseases during However, trisomy X is a relatively common pregnancy should prompt the investigation of aneuploidy and we suggest that this association characteristic abnormalities associated with is likely to be a chance event. The finding of DGS. These associated anomalies are, how- this anomaly might be an indication for prena- ever, difficult to detect by prenatal diagnosis. tal diagnosis in a subsequent pregnancy. The discovery during pregnancy of a These findings highlight the importance of conotruncal heart defect associated with a performing traditional cytogenetic analysis and 22q 1 deletion might indicate a severe form of FISH for suspected DGS during pregnancy this syndrome, which is known to show great when ultrasound studies show a conotruncal phenotypic variability. The most severely af- cardiac defect. In these cases prenatal diagnosis fected patients have serious, life threatening of a molecular deletion in the DGS critical heart defects and die neonatally. The least region of chromosome 22 suggests the exist- severely affected patients have only mild facial ence of associated anomalies and risks of anomalies and some developmental delay, but developmental delay. However, counselling no heart defects.'6 However, most of the remains difficult in view of the clinical variabil- 168 Portnoi, _Joyi, Gonzales, et al

ity described in DGS, where the phenotype detection of trisomy 21 and translocations of chromosome 4. Proc Nad Acad Sci USA 1988;9:138-42. cannot be accurately predicted from the geno- 10 Van Hemel JO, Schaap C, Van Opstal D, Mulder MF, Nier-

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