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279
A partial trisomy 9 case with dicentric chromosome
İstanbul Tıp Fakültesi Dergisi • J Ist Faculty Med 2022;85(2):279-84
Corresponding author/İletişim kurulacak yazar: meral25@yahoo.com, karaoguz@gazi.edu.tr
Submitted/Başvuru: 20.12.2021 • Revision Requested/Revizyon Talebi: 17.01.2022 •
Last Revision Received/Son Revizyon: 08.02.2022 • Accepted/Kabul: 08.02.2022 • Published Online/Online Yayın: 11.03.2022
CASE REPORT / OLGU SUNUMU
DOI: 10.26650/IUITFD.1038997
İst Tıp Fak Derg 2022 / J Ist Faculty Med 2022
A PARTIAL TRISOMY 9 CASE WITH DICENTRIC CHROMOSOME
DUE TO THE ADJACENT-2 SEGREGATION OF MATERNAL
RECIPROCAL TRANSLOCATION
MATERNAL RESİPROKAL TRANSLOKASYONUN ADJACENT-2 SEGREGASYONUNA
BAĞLI OLUŞAN DİSENTRİK KISMİ TRİZOMİ 9 OLGUSU
Ezgi URTEKİN1 , Gülsüm KAYHAN1 , Elvin KAZANCIOĞLU1 , Meral YİRMİBEŞ KARAOĞUZ1
1Gazi University, Faculty of Medicine, Department of Medical Genetics, Ankara, Turkiye
ORCID IDs of the authors: E.U. 0000-0001-9951-2812; G.K. 0000-0002-4286-243X; E.K. 0000-0002-7603-6558;
M.Y.K. 0000-0002-0178-8018
Cite this article as: Urtekin E, Kayhan G, Kazancioglu E, Yirmibes Karaoguz M. A partial trisomy 9 case with dicentric chromosome due
to the adjacent-2 segregation of maternal reciprocal translocation. J Ist Faculty Med 2022;85(2):279-84. doi: 10.26650/IUITFD.1038997
Content of this journal is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
ABSTRACT
Duplication of the short arm (p) of chromosome (Chr.) 9 is a fre-
quently seen abnormality while duplication of both p and long
arm (q) is a rare chromosomal rearrangement derived most-
ly from parental translocations or inversions. The unbalanced
products of the translocations are mostly derived from the 2:2
segregation of adjacent-1 division while the ones due the adja-
cent-2 patterns are rare. Here, a dysmorphic infant with a pure
duplication of 9pter to 9q22.31 is reported due to the product
of the adjacent-2 segregation of maternal reciprocal translo-
cation between the 9q22.31 and 22p11.1. The affected infant
had two normal and one derivative/dicentric Chr.9 (carrying the
centromere regions of both Chr.9 and Chr.22) with one normal
Chr.22. These results were confirmed by the fluorescence in situ
hybridization technique. Array-comparative genomic hybridiza-
tion confirmed the breakpoints precisely and revealed a 61.75
megabases duplication of Chr.9 consisting of many genes such
as BICD2, NTRK2, HNRNPK, and SMARCA2, which are mostly
related to developmental delay and growth retardation. Addi-
tionally, the infant had ear abnormalities, microcephaly, and ex-
tremity abnormalities, which were the other findings of trisomy 9.
In sum, the case has presented as a rare example of adjacent-2
division of 2:2 segregation and a pure partial trisomy of 9pter
to 9q22.31.
Keywords: Partial trisomy 9, reciprocal translocation, adjacent-2
segregation, dicentric chromosome, chromosomal rearrange-
ment, growth retardation, fluorescence in situ hybridization, ar-
ray-comparative genomic hybridization
ÖZET
Kromozom (Chr.) 9’un kısa koluna (p) ait duplikasyon sık olarak
görülmekle birlikte hem kısa hem de uzun kolun (q) duplikasyonu
daha çok ailesel translokasyonlar ve inversiyonlara bağlı oluşan
ve nadir olarak görülen bir kromozomal yeniden düzenlenmedir.
Ailesel translokasyonlara bağlı oluşan dengesiz gebelik ürünleri
daha çok 2:2 segregasyonun adjacent-1 aktarımı ile oluşmakta
iken, adjacent 2 aktarımı nadir bir durumdur. Bu çalışmada, an-
nenin 9q22.31 ve 22p11.1 bölgeleri arasındaki resiprokal trans-
lokasyonuna bağlı 9pter ile 9q22.31 bölgeleri arasında duplikas-
yonu olan dismorfik bir çocuk sunulmaktadır. Etkilenmiş çocuk
iki normal Chr.9, bir derivatif/disentrik Chr.9 (hem Chr.9, hem de
Chr.22’nin sentromerini taşıyan), bir tane de normal Chr.22’ye sa-
hiptir. Tüm bu sonuçlar floresan insitu hibridizasyon tekniği teyit
etmiştir. Kırık bölgelerini doğru olarak belirleyen array-karşılaştır-
malı genomik hibridizasyon tekniği BICD2, NTRK2, HNRNPK ve
SMARCA2 gibi büyüme gelişme geriliğine eşlik eden genleri de
kapsayan kromozom 9’a ait 61,75 megabazlık duplikasyonu orta-
ya çıkarmıştır. Ek olarak mikrosefali ve ekstremite anomalileri gibi
trizomi 9’a eşlik eden diğer bulgular da olguda bulunmaktadır.
Özetle bu olgu, adjacent-2 tipi segregasyonun ve sadece 9pter-
9q22.31 bölgelerini kapsayan kısmi trizomi 9’un nadir bir örneği
olarak sunulmaktadır.
Anahtar Kelimeler: Kısmi trizomi 9, resiprokal translokasyon,
adjacent-2 segregasyonu, disentrik kromozom, kromozomal ye-
niden düzenlenme, büyüme geriliği, floresan in situ hibridizasyon,
array-karşılaştırmalı genomik hibridizasyon
280
A partial trisomy 9 case with dicentric chromosome
İstanbul Tıp Fakültesi Dergisi • J Ist Faculty Med 2022;85(2):279-84
INTRODUCTION
Complete trisomy 9 is a quite rare but well-known
syndrome with distinctive clinical features, with more
than 150 cases reported in the database of the National
Organization for Rare Disorders (NORD) up to today
(1). The vast majority of the cases are mosaic due to the
postzygotic error at any time in early development, or,
rarely, due to the meiotic nondisjunction with subsequent
loss of the trisomic cell line. The assumed complete
trisomy 9 is a rare aneuploidy (which might represent a
sampling error of variable tissue mosaicism) that is worthy
of consideration (2). The partial trisomy of chromosome
(Chr.) 9 (involving short; p and/or long; q arm) is mostly
derived from a parental reciprocal translocation and is
accompanied by a concurrent deletion or duplication of
another chromosome due to the 2:2 or 3:1 segregation
mechanisms (2, 3). The present partial trisomy 9 (pter
to q22.31) case resulted from adjacent-2 segregation
of the maternal reciprocal translocation between Chr.9
and Chr.22. Since the breakpoint was at the centromere
of the Chr.22, the derivative chromosome 9 had two
centromeres, and a dicentric chromosome [dic(9;22)]
had been formed. This rare reciprocal translocation was
inherited to the child with adjacent-2 segregation, which
led to disomy 22 and partial trisomy 9 (pter to q22.31) and
this unique case gave us the opportunity to delineate
the accurate genotype-phenotype correlation of the
duplication for this relevant segment of chromosome 9.
Furthermore, we believe that this case will increase the
familiarity of the geneticist with the unusual segregation
pattern and also emphasize the importance of the usage
of different techniques such as cytogenetic, fluorescence
in situ hybridization (FISH) and array-comparative
genomic hybridization (array-CGH) studies to determine
the breakpoints of the chromosomal rearrangements.
CASE PRESENTATION
The 13-month-old girl patient was the first child born to
a non-consanguineous 27-year-old mother and a 34-year-
old father. At the 36th week of pregnancy, oligohydram-
nios was detected and an emergency C-section delivery
was performed. At birth, her measurements were in the
normal range for her birth week: 2160 g weight (10th cen-
tile), 44 cm length (10-25th centile), and 33 cm head cir-
cumference (75th centile). After the birth, the hypotonic
baby was hospitalized in the neonatal intensive care unit
for 53 days and was intubated for 23 days due to respi-
ratory distress syndrome. One month after she was dis-
charged from the hospital she started vomiting 6-7 times
a day, and her weight gain stopped after the 7th month.
Developmental milestones were delayed: she was able
to hold her head up at the age of 8 months. Physical
examination at 13 months of age revealed that her
measurements were small for her age (6200 g weight
(3.47 SD), 68 cm length (-2.81 SD) and 40.5 cm head
circumference (-4.81 SD). Brachydactyly was found (hand
8 cm and 3rd finger 3 cm, below the lowest percentile
line). She had microcephaly and facial dysmorphic
features such as hypertelorism, low set and cup-shaped
ears, broad nasal root and bulbous nose, low hanging
columella, short philtrum, thin and tented upper lip,
and downturned corners of the mouth (Figure 1a, b).
She also had a single transverse palmar crease in both
hands and fifth finger clinodactyly. Both of her second
toes were shorter than the others, and both of her feet
were deviated laterally (Table 1). She could not sit without
assistance, talk, or walk at time of physical examination.
Abdominal ultrasonography (USG) at two months showed
mild renal pelvis dilatation with renal pelvic AP with a
diameter of 4-4.5 mm. Brain MRI findings were compatible
with ventriculomegaly, which was evaluated as benign
Figure 1: Dysmorphic signs of the patient (a,b):
hypertelorism, bulbous nose, broad nasal root, low
hanging columella, short philtrum, tented upper lip,
downturned corners of the mouth, cup shaped ears
281
A partial trisomy 9 case with dicentric chromosome
İstanbul Tıp Fakültesi Dergisi • J Ist Faculty Med 2022;85(2):279-84
Table 1: The comparison of the clinical findings, conventional cytogenetic and array studies in patients with partial trisomy 9 (pter to q22~q32)
Karyotype Chromosome
9 duplicated
region
Other
duplicated
or deleted
region
Array Facial dysmorphism Other clinical
findings Extremity
abnormalities Radiological
findings Age
Present case 46,XX,+9,dic(9;22)
(9pter→9q22.31::
22q11.1→22qter)
mat
Trisomy 9pter to
9q22.31 No other
chromosomal
trisomy or
monosomy
arr[hg19]
9p24.3p13.1
(211,086-
38,741,437)x3,
9q21.11q22.31
(71,069,763-
94,291,138)x3.
hypertelorism,
esotropia, bulbous
nose, broad nasal root,
low hanging columella,
short philtrum, tented
upper lip, downturned
corners of the mouth,
cup shaped ears
hypotonia,
developmental delay,
growth retardation,
sacral dimple
laterally deviated
feet, joint laxity,
brachydactyly,
bilateral single
transverse palmar
creases, clinodactyly
of fifth finger,
relatively shorter
second toes
Abdominal US: mild
renal pelvis dilatation
and renal stones
ECHO: mitral valve
prolapse, secundum
atrial septal defect
Brain MRI:
ventriculomegaly
15 months
old (living)
Dhangar S, et
al. (2019) 46,XY,+der(9)
t(9;14)(q22.1;q11.2)
pat,-14
Trisomy 9pter to
9q22.1 Monosomy
14pter to
14q11.2
arr(GRCh38)
9p24.3q22.1
(203861-
87860633)x3 pat
Mild macrocephaly,
prominent forehead,
low hair line, downward
slanting of the eyes’
epicanthic folds,
hypertelorism, low set
ears, large pinnae, long
face, bulbous nose, thin
upper lip, long philtrum,
high arched palate
webbed neck,
kyphoscoliosis,
pilonidal sinus, delayed
speech development
and poor fine motor
development, bilateral
hearing loss
rocker bottom
feet, short middle
interphalangeal
elevated foot,
clinodactyly of fifth
finger
MRI and CT scan of
brain: generalized
cerebral atrophy,
dilated ventricles and
arachnoid cyst
2D-ECHO: tiny patent
ductus arteriosus
US of abdomen: small
size of both kidneys
5 years old
(living)
von
Kaisenberg
CS, et al.
(2000)
47,XX,+der(9)t(7;9)
(q35;q22.2)mat Trisomy 9pter to
9q22.2 Trisomy 7q35
to 7qter N/A micrognathia,
hypertelorism, deep-
set, posteriorly rotated
ears, bulbous nose
postmortem
examination: caudal
hypoplasia and
dysplasia of the
cerebellar vermis,
dilated foramen
Magendie, enlarged
cisterna magna
micropolygyria female
sex abnormalities
bilateral simian
creases US at 23 weeks of
gestation: hypoplasia
of the cerebellar
vermis, marginal
dilatation of the
cisterna magna and
the lateral ventricles
X-ray: presence of
only 11 ribs
23 weeks of
gestation
(termination
of
pregnancy)
Sutherland GR
et al. (1976)-
Case1
47,XX,+der(9),t(7;9)
(p22;q32)mat Trisomy 9pter to
9q32 Trisomy 7pter
to 7p22 N/A microcephaly, low
hair line, low set
ears, micrognathia,
hypertelorism,
microphthalmos,
pinpoint pupils, large
mouth, downturned
corners of the mouth
widely open sagittal
suture, palpable
metopic suture, short,
prominent sternum,
sacral dimple
Autopsy findings:
persistent left superior
vena cava, patent
ductus arteriosus,
bilobed right lung,
small kidneys,
hypoplastic cerebellar
vermis, dilated fourth
ventricle
flexion deformities
of the arms and
hands, bilateral
simian creases,
absence of the
terminal phalanges
of the thumb and
index fingers,
hyperconvex nails,
fixed dislocation
of the hips,
unstable dislocated
knees, talipes
calcaneovalgus
bilateral hypoplasia of
the pubic bones and
an angulated ischia,
dislocation of the
head of the radius,
hypoplasia of the
distal humerus and
fibulae, hypoplasia
of the ala of the
sacrum with poorly
developed sacro-iliac
joints
17 days
(exitus)
Lopez-Felix J,
et al.(2017) 47,XX,+der(9)t(8;9)
(p21.3;q22.3)mat Trisomy 9pter to
9q22.3 Trisomy 8pter
to 8p21.3 N/A Absent nasal bone claw-like hands US at 15.1 weeks
of gestation: CRL
(crown-rump length)
of 77.6 mm (which
accorded to 13.6
gestational weeks)
US at 20 weeks of
gestation: a fetus of
18 weeks, thickness
and dilatation of
right cardiac walls,
echogenic focus in
left ventricle
20 weeks of
gestation
(termination
of
pregnancy)
Metzke-
Heidemann
S, et al.
(2004)-patient 2
47,XX,+der(9)t(7;9)
(q35;q22.2)mat Trisomy 9pter to
9q22.2 Trisomy 7q35
to 7qter N/A Unilateral cleft lip and
cleft of both hard and
soft palate
N/A N/A N/A N/A
282
A partial trisomy 9 case with dicentric chromosome
İstanbul Tıp Fakültesi Dergisi • J Ist Faculty Med 2022;85(2):279-84
external hydrocephalus. An echocardiogram at ten
months revealed a mitral valve prolapse and secundum
atrial septal defect (Table 1).
Cytogenetics and molecular cytogenetics
Cytogenetic analysis was performed in the proband
and later in the parent with their consent (4). Proband
karyotype was 46,XX,+der(9)(9pter->9q22.31::22q11.1-
>22qter),-22. Paternal cytogenetic analysis revealed a
normal result (46,XY), while the mother had a reciprocal
translocation between Chr.9 and Chr.22 [46,XX,t(9;22)
(q22.31;q11.1)] (Figure 2a, 2b) (Table 1).
FISH analyses were carried out for both the proband
and the mother using the centromere, telomere (9p:
pVYS234B, 9q: pVYS235B) and whole chromosome
painting probes of Chr.9 and Chr.22 (Cytocell, Cambridge
UK), and ToTelVysionTM Multi-colour DNA probe mixture
3 [(22q11 (LSI bcr), 22qter (pVYS207M)] with chromosome
3pter and 3qter as controls)] (Vysis, Downer’s Grove,
IL, USA) (Figure 2c, d). The existence of centromere
region of Chr.22 (p11.1q11.1) on derivative Chr.9 was
detected via FISH analysis (Figure 2c, d), and the final
karyotype of the proband with dicentric chromosome
was 46,XX,+9,dic(9;22)(9pter→9q22.31::22p11.1→22qter)
mat,.ish dic(9;22)(9pter+,9qter-, D14Z1/D22Z1+,LSI
BCR+,22qter+,wcp22+) (Figure 2b, d). Array-CGH
(Human Genome G3 SurePrint 8x60K ISCA Array;
Agilent Technologies, Santa Clara, California)
confirmed the breakpoints of the alteration and
revealed a duplication in size of 61.75 megabases of
Chr.9, consisting of the BICD2, NTRK2, HNRNPK and
SMARCA2 genes with no gain or a loss of chromosome
22 [(arr[hg19] 9p24.3p13.1(211,086-38,741,437)x3,9q21.1
1q22.31(71,069,763-94,291,138)x3] (Figure 3).
DISCUSSION
After the first example of trisomy 9 shown via quinacrine
mustard fluorescence and trypsin banding techniques by
Feingold and Atkins in 1973, numerous cases of partial
trisomy 9 with a concomitant partial monosomy/trisomy
Figure 2: Partial karyotypes and FISH images of mother and proband. Partial karyotype
of the mother showing the breakpoints of normal and derivative (der) chromosome 9s and
22s (a), partial karyotype of the proband showing two normal and one derivative
chromosome 9 and one normal chromosome 22 (b). Arrows indicate the breakpoint
regions. In figure 2c, the cep14/22 (red) painting of mother’s metaphase is demonstrated.
The occurrence of centromere region on der 9 (up) is confirmed via cep14/22 probe.
Arrows indicate der9 (up), normal 22 (down) and der22 (right middle). In figure 2d,
proband’s chr 22q11 (LSI bcr: blue), qter regions of ch22 (yellow) and whole chromosome
paintings of ch22 (green) are demonstrated on der9 (up) and normal chr22 (down) (the red
signals show the 3qter regions and green signals show the 3pter regions as control probes).
Arrows indicate der 9 (up) and normal 22 (down).
283
A partial trisomy 9 case with dicentric chromosome
İstanbul Tıp Fakültesi Dergisi • J Ist Faculty Med 2022;85(2):279-84
were reported (Table 1) (3, 5-9). In those cases, the phe-
notypic effects of the concomitant partial monosomy/
trisomy could not be excluded. However, the present
case was derived from the adjacent-2 of 2:2 segregation
in meiotic disjunction of maternal translocation and her
clinical findings were demonstrative for pure duplication
of 9pter to 9q22.31 without any other concurrent imbal-
ance. Contrary to what is known about the dicentric chro-
mosomes, which are almost always unstable in the cell di-
vision with the centromeres pulled to the opposite poles
of the cell at anaphase, dicentric chromosome [dic(9;22)]
of our case was stable in the cell cycles. The steadiness
of this chromosome might be because of the formation
of a pseudo dicentric chromosome in which only one
centromere is active, and presumptively the active cen-
tromere belongs to Chr.9 (10).
The present case (adjacent-2 segregation product) is
one of the few options for the infant to be born alive
with dysmorphic signs as adjacent-1 segregation will
be ended with the trisomy/monosomy of Chr.22 with
a partial deletion/duplication of chromosome 9. In 3:1
segregation, there are two options of disomy 22 with
duplication and deletion of Chr.9 derived from tertiary
monosomy/trisomy segregation pattern, while the vast
majority of the gestational products will be monosomic
or double trisomic for the chromosome 9 and 22 (inter-
change monosomy/trisomy products). The family was
informed about all the options of the segregation via
videotaping consultation, and notified about the preim-
plantation and prenatal diagnosis in future pregnancies
(11).
Low-set/malformed ear is a common facial abnormality
seen in almost all patients with the regular or partial triso-
my 9 cases, concordant with ours (Figure 1a) (2, 7, 12-14).
While our case and the Sutherland GR et al. case were
presented with microcephaly, the Dhangar S et al. case
had macrocephaly (Table 1) (3, 6). Different extremity de-
formities, most frequently talipes or rocker bottom feet,
were also reported in cases with complete or partial triso-
my 9 (2, 3, 6, 15). The present case had laterally deviated
feet, joint laxity, clinodactyly of fifth finger, and relatively
shorter second toes (2, 3). Hearth defects (valve defects
and atrial septal defects) were presented in those cases
and a mitral valve prolapse and a secundum atrial septal
defect were detected in our infant’s echocardiogram at
10 months of age (2, 13).
The genes located on the long arm of chromosome 9,
like BICD2, NTRK2, HNRNPK, and SMARCA2, which
are mostly associated with autosomal dominant devel-
opmental delay and growth retardation, were found to
be duplicated in our case. The BICD2 gene is associat-
ed with childhood-onset muscle weakness and atrophy,
while the HNRNPK gene is associated with a complex
syndromic neurodevelopmental disorder, which explains
hypotonia, delayed psychomotor development, and
the sacral dimple in our patient. SMARCA2 and NTRK2
genes are related to microcephaly, and our case also has
this finding (Table 1).
Figure 3: Array-CGH image of the proband. The breakpoint region is 9q22.31. There is a duplication of chromosome 9 (61,751 kilobases) but
no gain or loss of chromosome 22 (Human Genome G3 SurePrint 8x60K ISCA Array)
284
A partial trisomy 9 case with dicentric chromosome
İstanbul Tıp Fakültesi Dergisi • J Ist Faculty Med 2022;85(2):279-84
In conclusion, this case with pure partial trisomy of chro-
mosome 9 has allowed us to describe the accurate phe-
notype-genotype correlation of this duplication and the
proper counselling. It must be kept in mind that the iden-
tification of the breakpoints, the size of the duplication or
the deletion and the identification of the genes encom-
passed in the imbalances are important, and all labora-
tory techniques, such as cytogenetic analysis, FISH and
array-CGH studies, should be applied to get a reliable
result.
Informed Consent: Written consent was obtained from the par-
ticipants.
Peer Review: Externally peer-reviewed.
Author Contributions: Conception/Design of Study- M.Y.K.,
E.U.; Data Acquisition- M.Y.K., E.U.,E.K.; Data Analysis/Interpre-
tation- M.Y.K., E.U., G.K.; Drafting Manuscript- M.Y.K., E.U.; Criti-
cal Revision of Manuscript- M.Y.K., E.U., G.K.,E.K.; Approval and
Accountability- M.Y.K., E.U., G.K.,E.K.
Conflict of Interest: Authors declared no conflict of interest
Financial Disclosure: Authors declared no financial support.
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