Epigenotypeephenotype correlations in
E L Wakeling,1S Abu Amero,2M Alders,3J Bliek,3E Forsythe,1S Kumar,1D H Lim,4
F MacDonald,5D J Mackay,6,7E R Maher,4G E Moore,2R L Poole,6,7S M Price,8
T Tangeraas,9C L S Turner,7M M Van Haelst,10C Willoughby,11I K Temple,7,12
J M Cobben13
Background SilvereRussell syndrome (SRS) is
characterised by intrauterine growth restriction, poor
postnatal growth, relative macrocephaly, triangular face
and asymmetry. Maternal uniparental disomy (mUPD) of
chromosome 7 and hypomethylation of the imprinting
control region (ICR) 1 on chromosome 11p15 are found
in 5e10% and up to 60% of patients with SRS,
respectively. As many features are non-specific,
diagnosis of SRS remains difficult. Studies of patients in
whom the molecular diagnosis is confirmed therefore
provide valuable clinical information on the condition.
Methods A detailed, prospective study of 64 patients
with mUPD7 (n¼20) or ICR1 hypomethylation (n¼44)
Results and conclusions The considerable overlap in
clinical phenotype makes it difficult to distinguish these
two molecular subgroups reliably. ICR1 hypomethylation
was more likely to be scored as ‘classical’ SRS.
Asymmetry, fifth finger clinodactyly and congenital
anomalies were more commonly seen with ICR1
hypomethylation, whereas learning difficulties and referral
for speech therapy were more likely with mUPD7.
Myoclonus-dystonia has been reported previously in one
mUPD7 patient. The authors report mild movement
disorders in three further cases. No correlation was found
between clinical severity and level of ICR1
hypomethylation. Use ofassisted reproductive technology
in association with ICR1 hypomethylation seems
increased compared with the general population. ICR1
hypomethylation was also observed in affected siblings,
although recurrence risk remains low in the majority of
cases. Overall, a wide range of severity was observed,
particularly with ICR1 hypomethylation. A low threshold
for investigation of patients with features suggestive, but
not typical, of SRS is therefore recommended.
SilvereRussell syndrome (SRS) is characterised by
intrauterine growth restriction (IUGR), poor post-
natal growth, relative macrocephaly, triangular
facial appearance, asymmetry of the face and/or
limbs, and fifth finger clinodactyly.1e3In 1999,
Price et al4studied a cohort of 50 patients with SRS
and suggested criteria for diagnosis. However, the
relatively non-specific features of SRS present
a continuing challenge to clinical diagnosis and to
definition of its true spectrum and natural history.
SRS is genetically heterogeneous. The first
molecular abnormality identified in a significant
proportion of patients was maternal uniparental
disomy for chromosome 7 (mUPD7).5Evidence
suggests this is present in around 5e10% of
cases.6 7More recently, abnormalities of chromo-
some 11p15 have been described. Chromosome
11p15 contains imprinted genes implicated in fetal
growth, controlled by two imprinting control
regions (ICRs): the telomeric ICR1 regulates
expression of IGF2 and H19; the centromeric ICR2
controls expression of CDKN1C, LIT1 (KCNQ10T1)
and other genes. Disturbances of this region are
associated with the overgrowth disorder Beck-
witheWiedemann syndrome (BWS). Identification
of maternally derived chromosome11p15 duplica-
tions in growth-restricted individuals, some with
features of SRS,8 9led to further investigation of
this region in SRS.
In 2005, Gicquel et al10reported loss of paternal
methylation at ICR1 in five out of nine patients
with typical SRS features. This was associated with
biallelic expression of H19 and downregulated
expression of the growth promoter IGF2. Subse-
quent studies suggest that up to 60% of patients
depending on the clinical criteria used for selection
of cases.7 11To date only one patient has been
reported with a maternally derived duplication
restricted to ICR2.12
Initial reports of a relatively mild phenotype in
association with mUPD713have been corroborated
by more recent comparisons with patients with
spective analysis of all patients with mUPD7
published to date concluded that mUPD7 could not
methylation on clinical grounds alone.16Clinical
studies of several patient cohorts with ICR1
short stature, characteristic craniofacial features
and, often, asymmetry.11 14 15 18A minority of
patientshave less typical features.17 20 21Correlation
between the level of ICR1 hypomethylation and
the severity of SRS phenotype has been reported
in several studies,10 14 17 20although the majority
of these have relied on retrospective data, which
may be limited and/or incomplete. Comparisons
of patients with ICR1 hypomethylation and
mUPD7 are restricted by the small numbers of
patients in the latter group.
We report a prospective study of clinical features
among 64 patients with a positive diagnosis of SRS:
14 15However, retro-
14e19show in the majority
including a figure and table, is
published online only. To view
these files please visit the
journal online (http://jmg.bmj.
For numbered affiliations see
end of article.
Dr E L Wakeling, North West
Thames Regional Genetic
Centre), Level 8V, North West
London Hospitals NHS Trust,
Watford Rd, Harrow, Middlesex
HA1 3UJ, UK;
Received 17 March 2010
Revised 10 May 2010
Accepted 13 May 2010
Published Online First
3 August 2010
This paper is freely available
online under the BMJ Journals
unlocked scheme, see http://
760 J Med Genet 2010;47:760e768. doi:10.1136/jmg.2010.079111
20 with mUPD7 and 44 with 11p15 hypomethylation. Findings
in patients with mUPD and 11p15 methylation abnormalities
were compared, allowing features more characteristic of each
group to be defined. We also sought evidence of correlation
between the level of 11p15 hypomethylation and severity of
Sixty-four patients with either mUPD7 or 11p15 hypo-
methylation were ascertained, following referral to diagnostic
laboratories within the UK and the Netherlands for investiga-
tion of a possible diagnosis of SRS, growth restriction or
asymmetry. Molecular reports were obtained for all patients
confirming positive diagnosis. Patients and their parents
attended an appointment during which clinical information was
recorded on a standard proforma, and the patient was examined
and measured. To preserve consistency in recording of data, all
patients were seen by one or more of a small group of experi-
enced clinical geneticists (EW, MVH, DL, SP, CT, KT, JMC) with
a special interest in SRS. Subsequently, all data and clinical
pictures were evaluated by one coordinating clinical geneticist
(EW). Additional information was also obtained from the
hospital notes. Informed consent was obtained from all patients
and/or their parents, and the study was approved by the Trent
Research Ethics Committee.
DNA methylation of KCNQ1OT1 and H19 was measured in the
Academic Medical Centre, University of Amsterdam, the
Netherlands (laboratory 1; 21 patients), and, in the UK, the
Wessex Regional Genetics Laboratory (laboratory 2; 19 patients),
West Midlands Genetics Laboratory (laboratory 3; four patients)
and South West Thames Molecular Genetics Diagnostic Labo-
ratory (laboratory 4; three patients).
Methylation-specific multiplex ligation-mediated PCR anal-
ysis was the first-line test in laboratories 3 and 4, and the second-
line test in laboratories 1 and 2. The SALSA MLPA kit ME-030
(MRC Holland, Amsterdam, The Netherlands) was used
according to the manufacturer’s instructions.22In laboratories 1,
2 and 4, the cut-off for diagnosis of an epigenetic anomaly was
a peak height ratio of $1.3 at two or more adjacent probes, and
in laboratory 3 the cut-off was $1.25. Among 75 normal
controls, such a ratio was not observed at two or more adjacent
In laboratory 1, methylation-specific high-resolution melt
analysis (HRM-A) was used as first-line testing, as described.23
Hypomethylation was determined by visual comparison of case
and control samples, an abnormal peak shape being absent from
45 normal controls. In laboratory 2, methylation-specific PCR
(MS-PCR) was used as the first-line test, as described.24A peak
height ratio of 1.3 was taken as evidence of hypomethylation,
such a ratio not being seen among 120 normal controls. For both
HRM-A and MS-PCR, genomic DNA was bisulfite-modified
using the EZ and EZ Gold DNA modification kits (Zymo
Research, Orange, California, USA) according to the manufac-
turer’s instructions. In all laboratories, testing for uniparental
disomy of chromosome 11 was performed by standard analysis
of microsatellite markers including D11S2071, D11S4046,
D11STH, D11S1318 and D11SHBB.
Testing for uniparental disomy of chromosome 7 was
performed by microsatellite analysis in laboratories 1e4 (13
patients) and a further six NHS service laboratories in the UK
(eight patients). In laboratories 1e4, a minimum of six markers
were used, including at least two each on 7p and 7q. Exclusion of
mUPD7 required evidence of biparental inheritance at two or
more markers, whereas a positive diagnosis required evidence of
uniquely maternal inheritance of two or more markers. In the
remaining laboratories, data from diagnostic reports confirmed
that a minimum of three microsatellite markers were tested,
with positive diagnosis requiring evidence of uniquely maternal
inheritance of at least two markers.
Patients were scored using the five key criteria (birth weight
#?2 SD from mean; poor postnatal growth #?2 SD from
mean; preservation of occipitofrontal circumference; classic
facial features; asymmetry) suggested by Price et al.4Patients in
our study found to have at least four of these features were
described as having ‘classical’ SRS. Limb asymmetry was scored
as present if there was $1 cm arm and/or leg length difference;
facial asymmetry was scored subjectively.
Laboratory staff were blind to the clinical scoring/phenotype
of the patients tested. Scoring was carried out by one of the
investigators not involved in examination of the patients and
also blind to the methylation index results (SK).
Statistical comparisons between the two molecular subgroups
were made using the Fisher exact test, the unpaired t test and
the ManneWhitney test, as appropriate. Correlation of meth-
ylation index with a number of clinical parameters was analysed
using Pearson correlation, Spearman’s rank correlation and the
unpaired t test, as appropriate. Statistical significance was set at
A total of 64 patients were included in this study: 44 with11p15
methylation abnormalities and 20 with mUPD7. The mean age
in the two groups was similar: 6.3 years (range 0.8e26.8) for
ICR1 hypomethylation; 7.3 years (range 1.3e17.9) for mUPD7.
The majority of patients with abnormal 11p15 methylation
had abnormalities restricted to ICR1. One patient reported on
previously was known to have mosaic mUPD11,25and two
more had maternal duplication of ICR1 and ICR2 (see supple-
mentary text and figure 3 online). All three of these patients
have typical SRS features.
In one family an affected brother and sister were found to
have ICR1 hypomethylation. Their parents and two other
unaffected siblings had normal methylation patterns.
Of the patients with ICR1 hypomethylation, 61% had at least
four of the five key features, compared with just 20% of patients
with mUPD7 (p¼0.003). The mean scores for patients with
ICR1 hypomethylation and mUPD7 were 3.7 and 3.0, respec-
tively. However, the greatest range in severity was associated
with ICR1 hypomethylation (range 2e5, compared with 2e4
for mUPD7). Four (9%) patients with ICR1 hypomethylation
and five (25%) with mUPD7 had just one or two of these
features. Of these, four were referred for testing on the basis of
asymmetry (hemihypotrophy) and five due to prenatal and/or
postnatal growth failure.
Two patients with normal growth parameters were referred
for investigation of asymmetry. One patient with mUPD7 had
typical facial features, but birth weight ?1.53 SD and height
?1.3 SDat 7 years. Another patientwith 11p15
J Med Genet 2010;47:760e768. doi:10.1136/jmg.2010.079111761
hypomethylation had fifth finger clinodactyly, but no other
features of SRS, with birth weight ?1.33 SD and height +0.2 SD
at 10 months.
The frequency of clinical features found in the two molecular
subgroups is summarised in table 1.
From maternal recollection, IUGR was suspected in 89% cases
with ICR1 hypomethylation and 70% with mUPD7 (p¼0.08).
In both groups, the average gestation at which IUGR was
detected was 23 weeks, probably reflecting the fact that most
women have anomaly scans at around this stage of pregnancy.
Overall, 78% of patients had a birth weight #?2SDS with
a wide range, particularly among patients with ICR1 hypo-
methylation (range ?4.88 to ?0.5 SD, mean ?2.49 SD). Patients
with mUPD7 had a mean birth weight of ?2.24 SD (range
?3.29 to ?1.29 SD). Birth weight was therefore more frequently
#?2SDS with ICR1 hypomethylation, whereas height at
examination was more frequently #?2 SDS with mUPD7.
In total, 30% of patients had received growth hormone.
Insufficient retrospective data were available to analyse the
difference in the effect of growth hormone treatment. In patients
not treated with growth hormone, those with ICR1 hypo-
height SDS than those with mUPD7 (78%) (p¼0.26). Eight
patients had reached their final height, five of which had been
treated with growth hormone (see supplementary table online).
Numbers were too small to allow meaningful analysis of the
effect of growth hormone on final height.
Global developmental delay was described in 34% cases. Severe
delay was uncommon, being described in only two children,
bothwith ICR1 hypomethylation.
following investigation for asymmetry. However, he was felt to
be very atypical for SRS, his growth parameters were normal,
and further investigation is ongoing to look for an additional
cause of his problems. The other had suffered a cardiac arrest at
9 months following repair of a ventricular septal defect. If these
two children are excluded from the analysis, moderate delay was
seen in one (2%) patient with ICR1 hypomethylation and two
(10%) with mUPD7. In the remainder, developmental problems
were mild. In those patients without global delay, gross motor
delay was still common, with mean age at walking of w20
months in both groups.
Behavioural problems were uncommon and mild. Three chil-
dren (one with mUPD7 and two with ICR1 hypomethylation)
were reported by their parents as being hyperactive. Only one
child had been referred for further assessment for behavioural
Major congenital abnormalities were markedly more common in
those patients with ICR1 hypomethylation (table 2). Campto-
dactyly was seen in 19% overall and appears to gradually prog-
ress in severity with age. Restriction of movement in other
joints was confined to patients with ICR1 hypomethylation.
Only upper limbs were affected, with four patients having
limited elbow extension bilaterally/unilaterally and one having
bilateral reduction of shoulder movements.
Excessive sweating was reported by 67% of parents. This may
have represented hypoglycaemia, but in most cases had not been
with hypomethylation of the imprinting control region (ICR) 1 and
maternal uniparental disomy of chromosome 7 (mUPD7)
Clinical features in patients with SilvereRussell syndrome
Male sex (%)
Age (years) (median (IQR))
Maternal age (years) (mean (SD))
Paternal age (years) (mean (SD))
History of infertility (%)
Assisted reproductive technology (%) 11
Placental abnormality (%)
Birth weight #?2 SD (%)
Height at examination #?2 SD (%)
Relative macrocephaly (%)*
Global delay (%)
Delayed motor milestones (%)
Speech delay (%)
Speech therapy (if $2.5 years) (%)
Statement of education (if $3.5 years)
Behavioural problems (%)
Congenital abnormalities (%)
Cleft palate/bifid uvula (%)
Congenital heart defect (%)
Male genital anomaly (%)
Renal anomaly (%)
Other skeletal abnormality (%)
Excessive sweating (%)
Feeding difficulties (%)
Gastro-oesophageal reflux (%)
Otitis media (%)
Delayed closure of fontanelles (%)
Movement disorder (%)
Triangular face (%)
Frontal bossing (%)
Irregular/crowded teeth (%)
Small teeth (%)
Down-turned corners of mouth (%)
Thin upper lip (%)
Low-set/posteriorly rotated ears (%)
Other clinical signs
5th finger clinodactyly (%)
2/3 toe syndactyly (%)
Joint contractures (%)
Cafe ´ au lait patches (%)
3.6 (1.8, 8.4)
6.4 (3.6, 10.1) 0.08
p Values in bold indicate significance.
*Head circumference $1 SDS above length SDS, measured at age of examination.
yExcluding those with global developmental delay.
762 J Med Genet 2010;47:760e768. doi:10.1136/jmg.2010.079111
formally investigated. Since there was no significant difference
in the frequency of documented evidence of hypoglycaemia in
either group, it is unlikely to account for the difference in rate of
global developmental delay.
Feeding difficulties were scored according to severity (1¼normal,
2¼mild, 3¼frequent/long feeds, 4¼prolonged nasogastric feeds,
5¼gastrostomy insertion). The average score for mUPD7 was
slightly higher than that for ICR1 hypomethylation (mean (SD)
4.7 (1.3) and 3.4 (1.4), respectively), although this did not reach
statistical significance (p¼0.48).
Intriguingly, one patient with mUPD7, aged 14.9 years, was
patient, aged 14.2 years, has a slight tremor affecting his left arm.
One further patient with mUPD7 had myoclonic jerks in infancy
(from 3 weeks to 1 year), which had subsequently resolved. No
patients with ICR1 hypomethylation had similar problems.
Figures 1 and 2 show facial features for many of the patients
with ICR1 hypomethylation and mUPD7 included in this study.
The photographs illustrate how facial features become less
striking with age. Owing to difficulties obtaining early pictures
and growth data from many of the older patients, clinical
features such as frontal bossing, triangular face and micro-
gnathia were scored according to the appearance of the patient
at examination (table 1). In addition, data were analysed for
triangular facies and frontal bossing in those patients under
5 years at examination. As expected, this showed increased
frequency of specific features at this age (triangular face in 67%
of ICR1 hypomethlyation and 100% of mUPD7; frontal bossing
in 81% of ICR1 hypomethylation and 67% of mUPD7).
Correlation with methylation index
Data on methylation index was available for 29 of the 44
patients with ICR1 hypomethylation. Clinical score, birth
weight SDS, postnatal height SDS, severity of feeding difficul-
ties, and the presence of developmental delay, asymmetry and/or
congenital anomalies were all analysed for correlation with level
of ICR1 hypomethylation. No evidence was found for correla-
tion between the level of ICR1 hypomethylation and clinical
severity (table 3).
Assisted reproductive technology (ART)
All five cases conceived as a result of in vitro fertilisation treat-
ment, including one via ovum donation and one via intra-
cytoplasmic sperm injection, were in the ICR1 hypomethylation
group. However, this difference between the groups did not
reach statistical significance.
Clinical diagnosis of SRS remains difficult, as many of its
features are non-specific, diagnostic criteria are not universally
agreed, and features are most striking in early childhood, making
assessment of older patients difficult. By collecting clinical data
from patients with a positive molecular diagnosis of SRS, we
were able to include patients irrespective of whether their
referring physician felt them clinically ‘typical’. This reduced
reporting bias. In contrast with previously published studies, our
data were gathered prospectively by a small number of experi-
enced geneticists, allowing both detailed and consistent analysis
of the phenotype.
Several scoring systems for clinical diagnosis of SRS have been
proposed.4 11 15Most recently, Bartholdi et al15developed criteria
to score 168 patients with suspected SRS, which were fulfilled
by all patients found to have ICR1 hypomethylation, but only
seven of 10 patients with mUPD7. These criteria could not be
applied in our study because data such as birth occipitofrontal
circumference and length were often unavailable, and the early
age of many participants precluded scoring for normal cognitive
development (defined as attending regular school). We therefore
used the criteria suggested by Price et al,4as complete data were
available for scoring in all patients. However, we recognise that
these criteria do not include feeding difficulties, which are
a major feature of this condition.
Clinical features in mUPD7 and ICR1 hypomethylation
Our study included sufficient patients with mUPD7 to allow
statistical comparison of features with ICR1 hypomethylation
cases. Consistent with other studies,11 14 15 17e19we found that
61% of patients with ICR1 hypomethylation had ‘classic’
features of SRS, compared with only 20% of patients with
Patients with ICR1 hypomethylation were less likely to show
postnatal reduction in height SDS than those with mUPD7,
although numbers were too small to reach statistical significance.
Binder et al19showed that children with mUPD7 have a signifi-
cantly higher birth length but lose height SDS post partum,
whereas those with 11p15 hypomethylation show no change in
height SDS. The same study noted a trend towards more height
gain with growth hormone therapy in children with mUPD7
than those with ICR1 hypomethylation.19In our study, insuffi-
cient data were available to test this observation. However, two
adults with ICR1 hypomethylation who had been treated with
growth hormone achieved final heights well within the normal
range. The possible differential effect of growth hormone in these
two subgroups is an important clinical question which deserves
further detailed and prospective investigation.
Asymmetry was significantly more common with ICR1
hypomethylation. This finding is in keeping with previous
reports4 13 15 16and may reflect mosaicism for hypomethylation
at the tissue level.
syndrome with hypomethylation of the imprinting control region (ICR) 1
and maternal uniparental disomy of chromosome 7 (mUPD7)
Congenital anomalies in patients with SilvereRussell
Palate Cleft palate (2)*
Bifid uvula (2)
Palatal insufficiency (1)
Ventricular septal defect (3)
Atrial septal defect (1)
Patent ductus arteriosus (1)
Bilateral undescended testes (3)
RenalHorseshoe kidney (1)
Unilateral renal dysplasia (1)
Skeletal Scoliosis (4)
Hip dysplasia (2)
Talipes equinovarus (1)
Radial hypoplasia, absent thumbs (1)
Limited elbow supination (1)
Iris coloboma (1)
Ileal insufficiency (1)
*Including patient with mosaic mUPD11.25
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We found psychomotor retardation in approximately one-
third of patients with SRS, in keeping with previous observa-
tions.26Patients with mUPD7 were more likely to have delayed
development and to have a statement of education. Global delay
was mostly mild, although moderate delay was more common
with mUPD7. Speech delay and referral for speech therapy were
more common with mUPD7, as reported in previous studies.13
This finding has been linked to the absence of paternal FOXP2
expression, as seen in other patients with developmental verbal
dyspraxia.27Early motor delay was also relatively common in
both groups and may result from a combined effect of low
muscle bulk and relatively large head size in infancy.
Feeding difficulties are well recognised as a major feature of
SRS.28Parents of children from both groups in this study often
commented on their lack of interest in sucking and absence of
hunger from birth.
In the SRS cohort of Price et al,422% had generalised camp-
todactyly. It has been hypothesised that this is specific to
patients with ICR1 hypomethylation.17Bruce et al14reported on
several patients with ICR1 defects and joint contractures
patients with hypomethylation of the
imprinting control region (ICR) 1 at
different ages. Group A: 1.4e3.3 years;
group B: 3.3e4.7 years; group C:
5.9e9.5 years; group D:
Facial appearance of
764 J Med Genet 2010;47:760e768. doi:10.1136/jmg.2010.079111
(including limited elbow extension) and/or other skeletal
abnormalities. In our cohort, limited elbow extension was seen
in four patients. Interestingly, one patient was found to have
radial hypoplasia. Although this feature is not usually associated
with SRS, at least one other patient with ICR1 hypo-
methylation has been described with thumb hypoplasia.14
In common with other studies,14major congenital anomalies
were significantly more common in patients with 11p15
involvement. Overall, major congenital anomalies appear to be
much more suggestive of, though not exclusive to, ICR1 hypo-
Importantly, we observed two teenage patients with mUPD7
and mild movement disorders; a further patient had a history of
myoclonic jerks in infancy. This is particularly interesting in
light of a recent report of myoclonus-dystonia in a patient with
mUPD7.29Myoclonus-dystonia typically presents before adult-
hood with mild dystonia (such as cervical dystonia or writer’s
cramp) and/or myoclonic jerks. The disorder is associated with
paternally derived mutations in the imprinted e-sarcoglycan
(SGCE) gene on chromosome 7q21. It may not previously have
been noted with mUPD7, as symptoms are relatively mild and
may start in later childhood. In addition, other genes may
modify the development of this condition, as has been noted in
dystonia due to DYT1 and DYT6 mutations.30
The ‘classical’ facial features of SRS (triangular-shaped face,
frontal bossing, down-turned corners of the mouth, and
patients with maternal uniparental
disomy of chromosome 7 with
increasing age. Group A:
1.3e3.8 years; group B: 4.0e7.9 years;
group C: 10.0e14.2 years.
Facial appearance of
J Med Genet 2010;47:760e768. doi:10.1136/jmg.2010.079111765
micrognathia) were apparent in many but not all patients in both
groups. One retrospective study suggested a higher frequency of
macrocephaly and frontal bossing in patients with ICR1 hypo-
methylation, and a higher incidence of triangular facies with
mUPD7.16These previous observations are supported by our
analysis of facial features in patients under 5 years.
It is well recognised that patients with BWS due to unipa-
rental disomy and imprinting defects of ICR1 are at increased
risk of embryonal tumours.31However, to date none of the SRS
patients with hypomethylation of H19 reported in this study
have developed tumours. Taken together with data from
previous studies,11 14 15 17 20there is currently no evidence for an
increased childhood tumour risk in patients with ICR1
Variation in severity of features
While most studies have found no evidence for ICR1 hypo-
methylation in cohorts of patients with isolated prenatal or
postnatal growth retardation,11 14 15 18incomplete SRS pheno-
type has been described with ICR1 methylation abnormality.17
20 21Patients presenting primarily with hemihypotrophy or with
mild prenatal and/or postnatal growth failure therefore form
part of the spectrum of ICR1 hypomethylation.
The range of phenotypic severity has been linked to the level
of ICR1 hypomethylation. Bruce et al14reported correlation of
severe ICR1 hypomethylation with the presence of asymmetry,
micrognathia and congenital anomalies. It was suggested that
35% of the variation in clinical severity could be explained by the
level of H19 hypomethylation. However, we found no statistical
correlation between methylation index and degree of clinical
severity in 29 patients studied.
Other factors may also influence the degree to which patients
with ICR1 hypomethylation are affected. Methylation status in
all our patients was analysed in DNA from blood lymphocytes,
but clinicalseveritymay reflect
methylation of either H19 or IGF2 in 11/42 and 3/42 patients,
respectively, associated with amelioration of phenotype. We had
insufficient molecular data to perform a similar analysis in this
study. Another potential explanation for the clinical variation
may be hypomethylation of multiple imprinted loci in some
patients.32Fourteen patients in this study were investigated for
hypomethylation of multiple imprinted loci, three of whom
showed additional methylation anomalies; the significance of
this remains to be determined.
Assisted reproductive technology
Several recent studies have reported an increased frequency of
ART conceptionsin childrenwith BWSor Angelman
syndrome.33These findings are consistent with reports of
imprinting defects in animal studies after in vivo embryo
culture. Evidence also exists for an increased frequency of ART in
association with SRS.34The general rate of ART is 1e3%, of
which low birth weight is a recognised complication.35In this
study, all five patients conceived as a result of ART had ICR1
hypomethylation (11% of this group), supporting an association
between ART and imprinting defects in SRS. There is evidence
that the increased incidence of BWS and Angelman syndrome
after ART is associated with fertility problems,36but patients
with SRS were not included in this study. Interestingly, the
reported rate of infertility (taking over 1 year to conceive) in our
two subgroups was similar (18% with ICR hypomethylation
and 20% with mUPD7). This suggests that ART may also have
a direct effect. However, much larger and more rigorous studies
are required to investigate this further.
The vast majority of cases of SRS are non-familial, but a few
exceptions are reported in the literature, notably those described
recently by Bartholdi et al.14One recurrence within affected
siblings was found in the present study. Microsatellite analysis
in the family was inconsistent with an imprinting centre defect
within 11p15. In another study, methylation analysis in sperm
from a patient with 11p15 hypomethylation showed a normal
sperm-specific methylation pattern with full methylation at
two loci within this region.19These findings suggest that
epimutation is reversed in the male germline. An alternative
explanation for recurrence, consistent with these findings, is an
inherited alteration of a trans-acting factor responsible for
maintenance of the imprint after fertilisation.
Only eight of our cohort had reached postpubertal age, possibly
reflecting several factors: molecular diagnosis of SRS has only
recently become widely available; SRS cases may become lost to
follow-up; and the characteristic features become less noticeable
with time. It has been hypothesised by Barker and Hales37that
the epidemiological association between poor fetal and infant
growth and the subsequent development of type 2 diabetes
results from the effects of poor nutrition in early life, which in
turn produces permanent changes in glucose/insulin metabo-
lism. However, there is, as yet, no evidence to suggest that
patients with SRS are at increased risk of developing type 2
diabetes or other metabolic problems in adulthood. In this study,
detailed endocrine work-up had only been carried out in one
adult patient (at 26 years). Longer-term, systematic endocrine
follow-up, looking for evidence of metabolic abnormalities in
patients with mUPD7, ICR1 hypomethylation and idiopathic
SRS will be important.
This study is restricted to SRS patients with known molecular
abnormalities. In w30% of patients with a clinical diagnosis of
SRS, the underlying molecular defect is unknown. Ideally,
molecular karyotype analysis should be carried out in patients
where the diagnosis of SRS is considered but mUPD7 and ICR1
hypomethylation have been excluded. Recent studies have
shown that a small proportion of such patients have cryptic
chromosome rearrangements.38However, they are often labelled
as ‘mild’ SRS, and this reinforces the importance of careful
clinical assessment to try to reduce the heterogeneity of patients
with idiopathic SRS.
imprinting control region (ICR) 1 with clinical severity
Correlation of level of hypomethylation of the
coefficient p Value
Analysis using Pearson correlation (*), Spearman’s rank correlation (y)
or unpaired t test (z).
ND, not determined.
766J Med Genet 2010;47:760e768. doi:10.1136/jmg.2010.079111
On the other hand, application of a strict scoring system risks
missing patients with either mUPD7 or a mild phenotype
associated with ICR1 hypomethylation. Only 61% of hypo-
methylation 11p15 and 20% of mUPD7 cases in our study
would have been diagnosed as ‘classical’ SRS according to the
criteria of Price et al.4No single clinical feature was present in all
cases and even low birth weight in only 78% overall. We would
therefore recommend a low threshold for investigation of SRS,
and, as it is difficult to differentiate between mUPD7 and ICR1
hypomethylation on the basis of clinical features alone, testing
for both should be carried out.
1North West Thames Regional Genetic Service (Kennedy-Galton Centre), North West
London Hospitals NHS Trust, Harrow, UK
2Institute of Child Health, University College London, London, UK
3Department of Clinical Genetics, Academic Medical Centre, Amsterdam, The
4Centre for Rare Diseases and Personalised Medicine and School of Clinical and
Experimental Medicine, College of Medical and Dental Sciences, University of
Birmingham, and West Midlands Genetics Service, Birmingham Women’s Hospital,
5Department of Medical and Molecular Genetics, School of Clinical and Experimental
Medicine, College of Medical and Dental Sciences, University of Birmingham, and
West Midlands Genetics Service, Birmingham Women’s Hospital, Birmingham, UK
6Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury, UK
7Division of Human Genetics, University of Southampton, School of Medicine,
8Department of Clinical Genetics, Northampton General Hospital, Northampton, UK
9Division of Pediatrics, Oslo University Hospital, Rikshospitalet, Oslo, Norway
10Department of Medical Genetics, University Medical Center, Utrecht, The
11DNA Laboratory, Medical Genetics Unit, St Georges Hospital, London, UK
12Wessex Clinical Genetics Service, Southampton University Hospitals Trust,
13Department of Pediatric Genetics, Emma Kinderziekenhuis AMC, Amsterdam, The
Acknowledgements We thank all the parents and children in the UK and the
Netherlands who have participated in the study. We are grateful to the many
clinicians who have helped recruit patients to the study and provided clinical data.
Hillary Bullman and Margaret Lever from Wessex Regional Genetics laboratory
tested many of the samples from patients in UK and provided useful feedback on
the paper. We also thank Paul Bassett for his clear statistical advice.
Funding Child Growth Foundation, 2 Mayfield Avenue, Chiswick, London W4 1PW.
Competing interests None.
Patient consent Informed consent was obtained from all patients/parents for
publication of photographs.
Ethics approval This study was conducted with the approval of the Trent Research
Provenance and peer review Not commissioned; externally peer reviewed.
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