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hypomethylation of the imprinted h19/igf2 locus in 11p15 and matupd7 are two major epigenetic etiologies in srs .
matupd7 was first reported by spence et al in a cystic fibrosis patient with srs like phenotype ( short stature and slight asymmetry ) .
after this paper , other cases affected by pre and postnatal growth retardation but not srs phenotype with matupd7 were published[46 ] .
the incidence of srs is approximately 1/3000 and more than 60 srs patients with matupd7 have been reported till the end of 2002[216 ] and matupd7 has been found in approximately 5 - 10% of srs patients with unexplained etiology .
after description of matupd7 srs cases , both arms of chromosome 7 were searched for candidate genes .
although 7p aberrations of four patients with a srs phenotype have been described , no pathogenic mutations have been identified in several studies focusing on the search for point mutations in 7p - encoded genes so far that might be functionally related to the srs phenotype . on the other hand , two papers published by hannula et al and reboul et al described srs cases with
a segmental maternal upd 7q showing the importance of human imprinted genes in 7q for human growth and srs .
however , screening studies on mutations in the imprinted genes and transcripts on 7q chromosome region failed to detect any pathogenic variants[2024 ] .
ring chromosome 15 , deletion of 15q , deletion of 8q11e13 , translocations associated with a breakpoint in 17q25 , deletion of csh1 , duplications of 11p15 , and epimutations of the imprinting center region 1 ( icr1 ) on 11p15 have been reported as the other reasons of srs .
loss of methylation of icr1 gene on 11p15 , resulting in a down - regulation of igf - ii and h19 genes which were found in 38 - 64% of cases with srs , have been reported as the most frequent reason in the etiology of srs as mentioned before[32 , 33 ] .
hypomethylation of matupd7 has not been studied in turkish population up to date so far .
therefore , to ascertain the frequency of matupd7 in the cause of srs in turkish population , we decided to screen matupd7 to perform genotype and phenotype correlation .
a total of 13 srs patients aged between 2 - 9 years , from two genetic subdivisions of the pediatric departments of two university medical school hospitals / turkey were included in this study .
diagnosis of srs was established in the patients according to the previously described in literature .
chromosomal analysis and subtelomeric fluorescent in situ hybridization ( fish ) ( telvysion probes ) ( vysis / abbott ) were performed to identify microscopic and submicroscopic imbalances on all patients .
the study was approved by the faculty ethics committee of the university . 
 dna preparation : dna
was extracted from 2 ml venous blood taken from all patients and their parents using ( dna isolation blood mini kit , invitek , germany ) standard procedures . 

genotyping for matupd7 in 13 srs patients was performed on all patients with different chromosome tetra and dinucleotide repeat microsatellite markers ( d7s460 , d7s821 , d7s1808 , d7s1818 , d7s1804 , d7s2195 and d7s2446 ) by polymerase chain reaction ( pcr ) ( abi pcr system 9700 ) .
pcrs were performed in 25l reaction containing 50ng dna , 1xdynazyme ii buffer , 1.5 mm mgcl2 , 300 um of each dntp , 0.3 um of each primer , 1% dimethyl sulfoxide , and 1.25 u taq dna polymerase ( fermantase , leon - rot , germany ) .
amplification was performed with an initial denaturation of 5 minutes at 94c , followed by 30 to 35 cycles each of 30 s at 94c , 75 s at 55c , and 60 s at 72c with a final extension at 72c for 10 minutes .
cases of matupd7 were genotyped for additional chromosome by 7 microsatellite markers , to verify matupd7 by pcr ( fig .
examples of str genotyping showing maternal uniparental heterodisomy 7 in srs patient . a : allelic patterns of the marker d7s821 .
chromosomal analysis and subtelomeric fluorescent in situ hybridization ( fish ) analysis were found to be normal in all patients .
clinical features of 13 srs patients including mat upd7 patient are given in table 1 .
there were no significant differences between clinical features of mat upd7 case and other srs cases except congenital heart defects .
echocardiographic studies revealed ventricular septal defect ( vsd ) , patent ductus arteriosus ( pda ) , and patent foramen ovale ( pfo ) in the patient with matupd7 . 
 
clinical features of silver - russell syndrome patients iugr : intrauterin growth retardation / pngr : postnatal growth retardation / chd : congenital heart defect the matupd7 case was a 2-year - old girl , the first child of non - consanguineous parents , born 5 weeks before term ( 33 weeks ) .
there was a history of fetal karyotyping because of intrauterine growth retardation which was found to be normal . on physical examination ,
her weight was 7500 gr ( <3 percentile ) , height 73 cm ( 3 - 10 percentile ) , and head circumference 48.5 cm ( 50 - 75 percentile ) .
she had relative macrocephaly , triangular face , broad prominent forehead , low set ears , downslanted corners of the mouth , micrognathia , clinodactyly of the 5th digit and bracydactyly as dysmorphological features ( fig .
facial features including relative macrocephaly , triangular face , broad prominent forehead , down slanted corners of the mouth , micrognathia and hemihypertrophy of the left side of the body are seen .
developmental milestones were as follows : sitting without support at age of 8 months , walking alone and speaking several words at age of 14 months .
it has been reported that matupd7 cases cover approximately 10% of all srs patients[8 , 9 ] . in the study
presented matupd7 was detected in 7.6% of srs patients , which is slightly lower than that in previous reports and this could be caused by the low number of srs patients in our study .
srs has variable characteristics , however it is easy to recognize with typical symptoms , but diagnosis may be difficult in milder cases .
our matupd7 patient presented with mild srs characteristics as the other matupd7 cases previously described ( table 2 ) .
matupd7 has been considered to be a subgroup among srs patients with mild dysmorphic features , severe feeding difficulties and delayed speech .
our patients represented the spectrum of dysmorphic features and developmental difficulties seen typically in patients with srs ( table 1 ) .
the dysmorphic features in matupd7 patients have been reported to be mild in both srs[8 , 16 , 34 ] and patients without srs , and these patients have also been defined as having intrauterine growth retardation ( iugr ) and postnatal growth retardation ( pngr ) with slight dysmorphic features .
it is often difficult to establish a diagnosis of a child with iugr , growth failure and dysmorphic features .
although growth retardation of unknown cause has been associated with upd , hannula et al showed that it is not worthwhile to screen those patients for matupd7 unless they show characteristic features of srs and severe growth retardation .
the matupd7 patient described here shows the fulfilling of diagnostic criteria for srs and supports the suggestion that matupd7 is not a general cause for growth retardation .
interestingly matupd7 was also reported in three patients with cystic fibrosis ( mim 219700 ) and unexpectedly severe short stature[3 , 5 , 12 ] . among these three cases one had growth hormone ( gh ) deficiency .
screening for matupd7 is therefore advisable if abnormally short stature occurs with cystic fibrosis or other recessive disorders mapped to chromosome .
although matupd and icr1 hypomethylation patients have overlapping features , asymmetry , fifth finger clinodactyly and congenital anomalies are more commonly seen in patient with icr1 hypomethylation , whereas learning difficulties and referral for speech therapy are more likely with matupd7 .
our matupd7 patient had mild dysmorphic features of srs that was similar to the patients previously described[8 , 9 , 11 ] . 

peg1/mest 
 [ 37 , 38 ] and cop35 both at 7q32 , and grb1036,37 at 7p11.2-p12,3 are the imprinted genes in srs that have been identified so far .
paternal mutation or a deletion in the related imprinting gene or genes presents with similar symptoms as in matupd7 patients . on the other hand ,
fetal growth regulator genes egfr ( epidermal growth factor receptor ) , 
 igfbp1 , and igfbp3 ( insulin - like growth factor binding protein 1 and 3 ) are the other candidate imprinting genes that were thought to be responsible in srs etiology .
congenital heart defects observed in this patient which has not been reported in matupd7 cases could be the result of one of these or other imprinted gene dysfunctions .
imprinting genes on chromosome 7 may be responsible for this additional anomaly or there may be coincidence .
methylation analysis indicated that in maternal but not paternal alleles , cpg islands are completely methylated in the promotor region , however , a recent study showed a de novo deletion in 7q32 affecting the paternal imprinted mest / peg1 gene copy .
it is generally diffucult to exclude mosaicism in an infant with upd in srs but it is identified in a patient related with relatively mild srs - like phenotype . in addition , iugr and prenatal abnormalities are associated with confined placental mocaicism ( cpm ) .
cpm is occasionally found with upd , where after a meiotic error leads to trisomy , followed by trisomic rescue leads to a upd cell line in the fetus .
therefore , in cases of upd originating from cpm , it is difficult to ascertain whether the growth retardation is caused by upd in the fetus , or the upd cell line or trisomic cell line in the placenta .
we coincidently ruled out cpm , by observing the normal karyotype after chorionic villus sampling with the indication of advanced maternal age .
one of the limitations in our study is the lack of evaluation of the other responsible etiologies , such as hypomethylation of the imprinted h19/igf2 locus , submicroscopic genomic alterations and mutations in the candidate genes .
matupd7 was detected in 7.6% of srs patients firstly in turkish population , which is slightly lower than that in previous reports .
it is also worth to emphasize that congenital cardiopathy of the matupd7 case has not been described in the literature to date .
we suggest testing all patients with intrauterine and severe postnatal growth retardation with only slight signs of srs .
objectivesilver  russell syndrome ( srs ) is a clinically and genetically heterogeneous syndrome which is characterized by severe intrauterine and postnatal growth retardation , and typical characteristic facial dysmorphisms . 
 it has been associated with maternal uniparental disomy ( upd ) for chromosome 7 and hypomethylation of imprinting control region 1 ( igf2/h19 ) in 11p15 . 
 upd refers to the situation in which both copies of a chromosome pair have originated from one parent . 
 upd can be presented both as partial heterodisomy and isodisomy . 
 the aim of this study was to determine the maternal upd7 ( matupd7 ) in 13 turkish srs patients.methodsgenotyping for matupd7 was performed with microsatellite markers by polymerase chain reaction.findingsthe maternal upd7 including the entire chromosome was identified in 1/13 ( 7.6% ) of individuals within srs patients . 
 there were no significant differences between clinical features of matupd7 case and other srs cases except congenital heart defects.conclusionit is often difficult to establish diagnosis of a child with intrauterine growth retardation ( iugr ) , growth failure and dysmorphic features . 
 thus , screening for matupd7 in iugr children with growth failure and mild srs features might be a valuable diagnostic tool .