Download Complex Chromosome Rearrangement of 6p25.3-.p23

Complex Chromosome Rearrangement of
6p25.3-.p23 and 12q24.32-.qter in a
Child With Moyamoya
abstract
A 7-year-old white girl presented with left hemiparesis and ischemic
stroke secondary to moyamoya syndrome, a progressive cerebrovascular occlusive disorder of uncertain but likely multifactorial etiology.
Past medical history revealed hearing loss and developmental delay/
intellectual disability. Routine karyotype demonstrated extra chromosomal material on 6p. Single nucleotide polymorphism microarray
revealed a previously unreported complex de novo genetic rearrangement involving subtelomeric segments on chromosomes 6p and 12q.
The duplicated/deleted regions included several known OMIMannotated genes. This novel phenotype and genotype provides information about a possible association of genomic copy number
variation and moyamoya syndrome. Dosage-sensitive genes in the
deleted and duplicated segments may be involved in aberrant vascular proliferation. Our case also emphasizes the importance of comprehensive evaluation of both developmental delay and congenital
anomalies such as moyamoya. Pediatrics 2013;131:e1996–e2001
AUTHORS: Rebecca E. Rosenberg, MD, MPH,a Maureen
Egan, MD,a Shaun Rodgers, MD,b David Harter, MD,b Rachel
D. Burnside, PhD,c Sarah Milla, MD,d and John Pappas, MDa
Departments of aPediatrics, bNeurosurgery, and dRadiology, New
York University School of Medicine and New York University
Langone Medical Center, New York, New York; and cLaboratory
Corporation of America, Center for Molecular Biology and
Pathology, Department of Cytogenetics, Research Triangle Park,
North Carolina
KEY WORDS
moyamoya, 6p trisomy, 12q deletion
ABBREVIATIONS
ACA—anterior cerebral artery
FISH—fluorescence in situ hybridization
HLA—human leukocyte antigen
ICA—internal carotid artery
MCA—middle cerebral artery
OMIM—Online Mendelian Inheritance in Man
SNP—single nucleotide polymorphism
Dr Rosenberg guided conception and oversight of manuscript
development and critically reviewed and revised manuscript for
intellectual content; Dr Egan collected data, reviewed literature,
and drafted the initial manuscript; Dr Rodgers collected and
analyzed data; Dr Harter analyzed data and reviewed
manuscript for intellectual content; Dr Burnside analyzed data,
including statistical analysis, and critically reviewed manuscript
for intellectual content; Dr Milla analyzed data; Dr Pappas
analyzed data, guided conception and oversight of manuscript
development, and critically reviewed manuscript for intellectual
content; and all authors approved the final manuscript as
submitted.
www.pediatrics.org/cgi/doi/10.1542/peds.2012-0749
doi:10.1542/peds.2012-0749
Accepted for publication Feb 27, 2012
Address correspondence to Rebecca Rosenberg, MD, MPH,
Department of Pediatrics, New York University School of
Medicine/NYU Langone Medical Center, 965-TH, 550 First Ave, New
York, NY 10016. E-mail: [email protected]
PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).
Copyright © 2013 by the American Academy of Pediatrics
FINANCIAL DISCLOSURE: The authors have indicated they have
no financial relationships relevant to this article to disclose.
FUNDING: No external funding.
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ROSENBERG et al
CASE REPORT
Although pediatric ischemic stroke is
an uncommon occurrence, moyamoya
is responsible for 6% of cases.1–3
Moyamoya is a cerebrovascular occlusive disorder characterized by
bilateral progressive stenosis and occlusion of the distal intracranial internal arteries (ICA) and the proximal
anterior and middle cerebral arteries
with development of compensatory
collateral vessels. The latter appear
radiographically as a “puff of smoke”
(moyamoya in Japanese).4–6 In juvenile
moyamoya, the most common initial
presentation is extremity weakness or
paralysis secondary to cerebral ischemia.4,7
Moyamoya was first codified in Japan in
1969.6 Patients are characterized as
having moyamoya syndrome if the
vascular findings are associated with
an underlying condition, including acquired disorders such as previous cephalic radiation therapy or infection
and genetic disorders, such as Down
syndrome, neurofibromatosis, sickle
cell anemia, and Alagille syndrome.2,8–10
Moyamoya disease, in contrast, generally refers to idiopathic or isolated, potentially familial, moyamoya.
Juvenile moyamoya incidence varies by
ethnicity (0.1/100 000 in Caucasian
children and 1/100 000 in Japan and
Korea) and gender (female: male 2:1)
with an overall higher prevalence in
families (6%–12%).10 Genetic influences in moyamoya have been studied in
twin, linkage, and identification analyses11,12 in various ethnic groups, but no
consistent finding has emerged.10,12
This suggests both heterogeneity and
epigenetic influences in moyamoya
among different ethnic groups, with
candidate mutations affecting human
leukocyte antigen (HLA)-related genes
(6p21),13 neurofibromatosis-linked genes
(17q25),14 and metalloproteinase inhibitor genes involved in collagen vascular architecture (3p24).15 Early-onset,
or juvenile, and late-onset moyamoya
PEDIATRICS Volume 131, Number 6, June 2013
likely have different etiologies, as suggested by HLA-related research in
Japan.16
Within moyamoya-related syndromes,
several are also associated with developmental delay. Developmental delay and intellectual disability affects 1%
to 3% of US children.17 The American
Academy of Neurology and American
Academy of Pediatrics recommends
evaluation, including genetic evaluation, of children and particularly those
with isolated cognitive delay because
of implications for prognosis, reproductive capability, and neurologic
progress.17,18 Genetic etiologies, including chromosomal and subtelomeric duplicated or deleted sequences,
can be identified in ∼20% to 40% of
cases.17,19 Previously, both 6p20 and
12q subtelomeric trisomies21 were
reported among genetic rearrangements associated with developmental
delay.
In this report, we describe a white child
with moyamoya syndrome and mild
developmental delay. High-resolution
single nucleotide polymorphism (SNP)
array, fluorescence in situ hybridization (FISH), and chromosome analysis
identified a de novo complex genetic
rearrangement: del 6p, dup 6p, and
dup12q. This particular unclassified
syndrome and genotype has not been
previously reported in the literature to
our knowledge.
CASE PRESENTATION
A 7-year-old white girl with moderate
bilateral conductive hearing loss and
developmental delay presented to her
pediatrician with a 1-day history of fever
to 103°F, cough, and congestion. She
progressed to persistent fever, chills,
vomiting, and inability to tolerate oral
liquids and was admitted to a community hospital for dehydration. The
physical examination on admission
was notable for a 3/6 systolic murmur
with subsequent unremarkable echocardiogram.
On day 4 of illness, the patient developed
acute left-sided hemiparesis and leftsided facial droop. Vital signs at that
time were temperature 99.8°F, 122/55
blood pressure, heart rate 102 beats/
minute, and respiratory rate 22 /minute. Her neurologic examination was
otherwise unchanged without clinical
seizures or change in mental status. A
noncontrast head CT was unremarkable.
The patient was started on ceftriaxone
for possible meningitis. White blood
count was 3.4 K/uL with hemoglobin of
12.5 g/dL. Analysis of cerebrospinal
fluid showed protein of 18 g/dL, glucose
of 70 g/dL, 2 leukocytes, 0 red blood
cells; Gram stain and culture were
negative. Liver enzymes, total protein,
albumin, partial thromboplastin time,
prothrombin time, and international
normalized ratio were all within normal
limits; C-reactive protein was 9 mg/L,
and erythrocyte sedimentation rate
was 10 mm per hour. On day 5 of illness,
an MRI of the brain without and with
contrast was performed. Diffusion
weighted imaging was consistent with
bilateral acute watershed infarctions in
the frontal lobe and white matter, with
the right hemisphere more affected
than left (Fig 1) and reduced diffusion
within the splenium of the corpus callosum (not shown). Intracranial magnetic resonance angiogram (Fig 2)
showed severe narrowing/occlusion of
the right supraclinoid internal carotid
artery (ICA) with no evidence of flow in
the A1 segment of the right anterior
cerebral artery (ACA). The M1 segment
of the middle cerebral artery (MCA) had
little to no flow; however, there was reconstitution of the M2 and distal segments of the MCA. MR angiogram of
neck showed no abnormality. IV steroids
were initiated for potential infectious
vasculitis. Additional workup for vasculitis including ACA, anticardiolipin
e1997
significant for an older, brother with
congenital intracerebral venous malformation who was otherwise healthy.
On the basis of this information, physical examination and vascular abnormalities consistent with Alagille
syndrome, patient and parent samples
were sent for chromosome analysis,
SNP microarray, and JAG1 gene sequencing (chromosome 20). Mutations
in the JAG1 gene are associated with
Alagille syndrome.
FIGURE 1
Brain MRI at presentation. A, Diffusion weighted imaging and B, apparent diffusion coefficient map,
demonstrate frontal lobe white matter reduced diffusion consistent with infarction in watershed
territories, right side greater than left.
antibodies, and anti-DNAse B were all
unremarkable.
sion, 81 mg ASA daily and activity restriction.
The patient was then transferred to our
institution for pediatric neurosurgical
evaluation and management. Neurologic examination demonstrated central left facial paresis and 0/5 motor
strength in left upper and lower extremity with Babinski sign on the left but
was otherwise unremarkable. Initial
treatment consisted of volume expan-
To differentiate vasculitis from moyamoya and plan for potential intervention,
the patient underwent conventional cerebral angiogram. Angiogram demonstrated bilateral ICA abnormalities, with
narrowing and occlusion of the right
supraclinoid ICA involving the right A1
segment of the anterior cerebral artery
and M1 segment of the MCA (Fig 3), with
similar but less severe left-sided involvement. Prominent tiny capsular
and lenticulostriate collateral vessels
suggested chronic vascular compensation consistent with moyamoya disease (Fig 3).
FIGURE 2
Two-dimensional time of flight magnetic resonance cerebral angiogram demonstrated right
supraclinoid ICA narrowing/occlusion (arrow).
Flow not seen in proximal M1 and A1 segments;
however, distal flow is seen in the right ACA and
MCA.
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ROSENBERG et al
Clinical genetics was consulted to
evaluate for a possible genetic syndrome. Findings included triangular
face with a wide forehead, long nose
with bulbous tip, short distal phalanges
with short nails but no hepatosplenomegaly. Review of medical history
revealed full-term, appropriate for
gestational age infant (2.9 kg) of nonconsanguineous parents of German
and Irish/Italian descent and neonatal
hyperbilirubinemia requiring phototherapy. She had bilateral ossicular
dysplasia causing moderate bilateral
conductive hearing loss and mild developmental delay. Family history was
JAG-specific sequencing and deletion/
duplication testing revealed no mutations and no variants of known significance.
Chromosome analysis was performed
on peripheral blood lymphocytes by
using standard protocols at the 500band level and revealed additional unidentified chromosome material on
distal 6p: 46XX, add(6) (p25). SNP
microarray and FISH revealed a complex chromosome rearrangement involving chromosomal segments of 6p
and 12q. SNP microarray analysis was
performed by using the Cytoscan HD
platform (Affymetrix, Santa Clara, CA).
The gene chip contains 743 000 SNP
probes and 1 953 000 NPCN probes
with a median spacing of 0.88 kb;
250 ng of total genomic DNA extracted
from lymphocytes was digested with
NspI and then ligated to NspI adaptors,
respectively, and amplified by using
Titanium Taq with a GeneAmp PCR
System 9700 (Applied Biosystems, Foster City, CA). Polymerase chain reaction
products were purified by using
AMPure beads (Agencourt Biosciences,
Beverly, MA) and quantified by using NanoDrop 8000 (Thermo Fisher,
Wilmington, DE). Purified DNA was
fragmented and biotin labeled and hybridized to the Affymetrix Cytoscan HD
GeneChip. Data were analyzed by using
Affymetrix Chromosome Analysis Suite
v.1.2. FISH was performed by using
commercially available subtelomere
probes from Abbott Molecular (ToTel
CASE REPORT
final karyotype of the patient is as follows: 46,XX,der(6)(12qter-.12q24.32::6p23.6p25.3::6p25.3-.6qter) with genomic
positions of 6p25.3(94 649-402 748)x1,
6p25.3p23(430 545-14 587 883)x3, 12q24.32q
24.33(124 782 854-132 287 718)x3. The
genomic coordinates are based on NCBl
genome build 36 (Supplemental Tables
and Figures). Both parents had normal
high-resolution karyotype (550 band
level). The duplication of 6p25.3-.p23
and the duplication of 12q24.32-.qter
were both visible cytogenetically; because parental karyotypes were normal, these abnormalities are de novo.
FIGURE 3
Digital subtraction cerebral angiogram demonstrating narrowing/occlusion of the right supraclinoid
ICA involving the M1 segment of the MCA (small arrows). The ACA is not opacified. Multiple capsular and
lenticulostriate collateral vessels (arrowhead) indicate chronicity typical for moyamoya disease/
syndrome. MCA is seen reconstituted distally (large arrow).
Mix 12, Abbott Molecular, Santa Clara,
CA) according to standard protocols
and counterstained with DAPI (Fig 4).
The exact rearrangement included
a 402 Kb terminal deletion at 625.3; an
inverted interstitial14.2 Mb duplication
of 6p25.3-.p23; and 7.6 Mb duplication
of 12q24.32-.qter localized to the terminal p arm of derivative chromosome
6, as confirmed by FISH analysis. The
During the remainder of hospital course
the patient received extensive physical
and occupational therapy including inpatient rehabilitation, with gradual
improvement of left hemiparesis to
preillness baseline. Three weeks after
discharge, the patient underwent bilateral pial synangiosis, a form of indirect bypass commonly used inpatients
who are symptomatic but clinically stable or whose only initial presentation is
headache or transient ischemic attack.4,7
The procedure was uncomplicated, and
the patient is currently doing well
FIGURE 4
A, Partial karyotype and composite ideogram of derivative chromosome 6. Breakpoints are depicted with red arrows with the composition of the segments
indicated to the right, proceeding centromeric -. telomeric, as indicated. Composite chromosome 6 was made using online tool by Hiller B, Bradtke J, Balz H,
and Rieder H: CyDAS Online Analysis Site, http://www.cydas.org/OnlineAnalysis. B, FISH using subtelomere probe set ToTel Mix 12 (12pter, green; 12qter, red; 18
centromere, aqua; 18qter, yellow; Abbott Molecular, Inc, Santa Clara, CA). Derivative chromosome 6 with 12qter signal indicated.
PEDIATRICS Volume 131, Number 6, June 2013
e1999
without any neurologic deficits. She
remains on daily aspirin therapy.
DISCUSSION
The acute and subacute management of
pediatric ischemic stroke secondary to
moyamoya is well documented.4 Additional assessment of risk and prognosis
is related to both underlying neurovascular pathology and any associated
syndromic comorbidities, such as in
Down syndrome or neurofibromatosis,
making clinical genetic evaluation helpful in discriminating between isolated/
idiopathic and disease-associated moyamoya.1,2,4,19 Moyamoya in the presence
of atypical facies and other medical
and developmental issues in our patient was associated with a previously
unreported unbalanced chromosome
rearrangement including partial subtelomeric trisomies at both 6p25.3-.
p23 and 12q24.32-.qter.
Although this particular structural
rearrangement has not been reported
before, both 6p and 12q partial trisomies have been reported, although
most duplications of 6p have been
larger and involve imbalance of other
chromosomes.20,22 The terminal 6p deletion of this patient includes a single
Online Mendelian Inheritance in Man
(OMIM) annotated gene, IRF4, which is
not known to be dosage sensitive. The
proximal duplication of interstitial 6p
includes 51 OMIM annotated genes,
including FOXC1, deletions and duplications of which have been associated
with ocular abnormalities and DandyWalker malformation.23,24 Although
6p25.3 deletion is a known clinical entity, our patient does not share characteristic brain or facial features
previously reported.25
The reported phenotype of partial trisomy 6p includes pointed chin, long
philtrum, low set ears, hearing loss and
developmental delay as in our patient
but also typically involves moderate to
severe ocular, cardiac and renal disease, and psychomotor delay.22,26,27 The
relative sparing of stigmata in our patient with only mild developmental delay and hearing loss despite the large
chromosome rearrangement is likely
due to variability of expression frequently seen in chromosome duplication syndromes.
The 12q region includes 22 OMIM annotated genes, none of which have been
associated with genetic disorders.
Partial trisomy of distal 12q has also
primarily been associated with imbalance of other chromosomes but generally includes dysmorphic features,
developmental delay, and intellectual
disability.28
Neither partial 6p25 trisomy nor partial
12q trisomy have been previously
reported with moyamoya or any other
cerebral vascular malformations. Genetic studies on juvenile moyamoya in
Japanese and Korean pediatric cohorts
correlate with specific HLA phenotypes
associated with chromosome 6p. The
HLA gene cluster is localized to 6p21.32,
which is not included in the rearrangement in our patient, although sequence
mutations cannot be ruled out.13,16 The
de novo structural rearrangement we
describe in this patient of western European descent may thus represent
a true phenotypic association of partial
trisomy 6p with moyamoya.
reassuring because developmental regression has not occurred, as is the case
with most of the patients with chromosome rearrangements. The presumed
de novo nature of the cytogenetic abnormality is useful information for
family planning for her parents and
brother.29
Second, this case contributes to the
small literature of juvenile moyamoya
genetic association in proximity to HLA
markers at chromosome 6p25. This
previously unreported complex genetic rearrangement is associated
with moyamoya, hearing loss, developmental delay, and Alagille-like
phenotype in a white child. Duplications of this nature, known as copy
number variants, often cause disease
through a dosage-sensitive mechanism, which can, among other mechanisms, affect regulation of other gene
expression.30 Further targeted and
renewed research is warranted at
these loci to examine the role of HLA
alleles in potential aberrant vascular
proliferation.1,2 The genetic causes of
the abnormal cerebral vessel intimal
thickening and disruption in moyamoya, regardless of associated disease, may offer clues to both pediatric
stroke and atherosclerotic disease
more broadly.10,11
Genetic evaluation yielded valuable
results on several levels. First, the
chromosomal abnormality is somewhat
Lastly, we confirmed the importance in
primary care of a comprehensive genetic evaluation for developmental
delay as well as complete genetic
evaluation of patients presenting with
moyamoya.17,18 In particular, the bilateral hearing loss, developmental
delay, and atypical facies in our patient warranted further chromosomal
analysis independent of moyamoya
presentation.
Young. Management of stroke in infants
and children: A scientific statement from
a special writing group of the american
heart association stroke council and the
council on cardiovascular disease in the
young. Stroke. 2008;39(9):2644–2691
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