Comparison of high resolution cytogenetics, fluorescence in situ hybridisation, and DNA studies to validate the diagnosis of Prader-Willi and Angelman's syndromes

Eighty seven referrals with Prader-Willi syndrome and 49 with Angelman's syndrome were studied. High resolution cytogenetics was performed on all probands. Molecular studies, performed on the proband and both parents in each case, utilised multiple probes from within and distal to the 15(q11-13) region in order to establish the presence of DNA deletion or uniparental disomy. In addition, FISH, with probes at D15S11 and GABR beta 3 from the Prader-Willi syndrome/Angelman's syndrome region, was performed on a subset of 25 of these patients. In the referral group with Prader-Willi syndrome, 62 patients had a normal karyotype and 25 were deleted on high resolution cytogenetics. Twenty nine were found to be deleted with DNA techniques. In the Angelman's syndrome group, 37 had a normal karyotype and 12 were deleted on high resolution cytogenetics while 26 were deleted on molecular studies. The diagnosis was reassessed in 35 referrals with Prader-Willi syndrome and 11 with Angelman's syndrome following a non-deleted, non-disomic result. Of individuals who were neither deleted nor disomic on DNA studies, a false positive rate of 11.4% (4/35) for Prader-Willi syndrome and 16.7% (2/12) for Angelman's syndrome was found for a cytogenetically detected deletion. The false negative rate for deletion detected on high resolution cytogenetics was 19.5% (12/62) for Prader-Willi syndrome and 35% (13/37) for Angelman's syndrome. Thus high resolution cytogenetics was shown to be unreliable for deletion detection and should not be used alone to diagnose either syndrome. There were no discrepancies with FISH in 25 cases when FISH was compared with the DNA results, indicating that FISH can be used reliably for deletion detection in both syndromes.     

Silver-Russell-Kleinwuchs

Silver-Russell syndrome (SRS) is characterised by severe intrauterine and postnatal growth retardation. Like Prader-Willi and Angelman syndrome it belongs to the increasing class of congenital imprinting disorders. Until recently, the clinical diagnosis of SRS could be confirmed by genetic testing in only <10% of patients. With the identification of disturbed methylation in 11p15 molecular confirmation of the diagnosis is now possible in a further ~38% of cases. In addition, an increasing number of submicroscopic chromosomal disturbances are described based on the application of molecular karyotyping (??DNA chips??). Meanwhile, the same epimutations have been reported in patients with different imprinting phenotypes; an isolated view on a single imprinting disorder is therefore complicated. The reason for this observation is currently unknown, but it seems that similar causes for this group of diseases exist. These causes as well as the pathogenic relationship between (epi)genotype and phenotype currently remain unclear. However, the clinical diagnosis can already be confirmed in ~50% of SRS patients.     

Clinical report—health supervision for children with Prader-Willi syndrome

This set of guidelines was designed to assist the pediatrician in caring for children with Prader-Willi syndrome diagnosed by clinical features and confirmed by molecular testing. Prader-Willi syndrome provides an excellent example of how early diagnosis and management can improve the long-term outcome for some genetic disorders.     

Congenital hypothyroidism with Prader-Willi syndrome

We report a 1 year-old female patient with severe hypotonia who has congenital hypothyroidism and Prader-Willi syndrome (PWS). At birth she was found to have congenital hypothyroidism caused by an ectopic sublingual thyroid gland and was commenced on thyroid replacement therapy. She continued to have severe motor delay and therefore further diagnostic evaluation was performed. PWS was confirmed by DNA and fluorescence in situ hybridization (FISH) analysis. This report emphasizes the need to further investigate patients who are found to have congenital hypothyroidism and do not improve adequately on treatment.     

Standards for selected anthropometric measurements in Prader-Willi syndrome

We report standards (95th, 50th, and 5th centiles) in Prader-Willi syndrome for weight, height, sitting height, head circumference, head length, head breadth, hand length, middle finger length, palm length, hand breadth, foot length, foot breadth, triceps skinfold, and subscapular skinfold. For comparison with Prader-Willi syndrome standardized curves, normal control data from the literature were plotted similarly and standard curves were produced. We encourage the use of these standards with the examination of patients who have Prader-Willi syndrome and in the comparison of the patient who has Prader-Willi syndrome with other similarly affected individuals. The standards may also be useful for assisting in the diagnosis of Prader-Willi syndrome, particularly in younger individuals.     

The diagnosis of Prader–Willi syndrome

The methylation test can make the diagnosis of Prader-Willi syndrome (PWS) in approximately 99% of patients and is confirmed as a reliable, robust screening test. In a patient with PWS, methylation analysis does not provide the mechanism, for which other different genetic tests are required. Appropriate tests are available in each Australian state.     

Physical features of Prader-Willi syndrome in neonates

A retrospective study of 16 patients was undertaken to identify physical features that may typify neonates with Prader-Willi syndrome. Several features known to be typical of Prader-Willi syndrome in early infancy were confirmed, including hypotonia and genital hypoplasia. A number of features that have not previously been emphasized as characterizing Prader-Willi syndrome were also identified, most notably abnormal cry and, in males, signs of genital hypoplasia but with an apparently normal phallus. Other features included disproportionately large head circumference, disproportionately large anterior fontanelle, mild micrognathia, mild anomalies of the gingivae or alveolar ridges, and changes in the appearance of the skin. Appreciation of these features may assist the pediatrician in recognizing the child with Prader-Willi syndrome during the neonatal period, before the appearance of better-known findings of later onset, such as obesity and acromicria.     

Prader-Willi Syndrome with del(15)(q1l, q13) Associated with Hepatoblastoma

A case of Prader-Willi syndrome who later developed hepatoblastoma is reported. Prader-Willi syndrome was suspected because of hypotonia, hypopigmentation, and undescended testes when he was a newborn infant. The diagnosis was confirmed by chromosome analysis, which showed 46XY del(15)(qll, ql3). When he was 1 year 4 months old, a liver tumor and high serum AFP were found. At operation a large tumor arising from the caudate lobe was found and the tumor was totally resected. After completion of the hepatectomy, he developed circulatory collapse of unknown cause and died shortly after the operation. Histopathologic examination revealed that the tumor was composed of two components, well differentiated cells and poorly differentiated cells. The well differentiated part did not dominate the poorly differentiated part, so it was diagnosed as poorly differentiated hepatoblastoma. This is the first reported case of Prader-Willi syndrome with a pediatric malignant tumor.     

Spontaneous growth in German children and adolescents with genetically confirmed Prader-Willi syndrome

Height and weight in children with Prader-Willi syndrome, diagnosed by standard clinical criteria, follow a specific developmental pattern resulting in early childhood obesity, absent pubertal growth spurt and adolescent short stature. New molecular techniques (methylation analysis, fluorescence in situ hybridization) now allow the unequivocal diagnosis of Prader-Willi syndrome (PWS). We investigated the possibility of a bias in syndrome-specific growth standards based on clinically diagnosed patients by comparing these standards with new standards derived from 100 German patients with molecularly confirmed PWS, none of whom had received a growth-promoting therapy. Height centile curves of the German patients fall in the tall range of standards derived from American patients. This is mainly due to an elevation of the lower centile ranges in both sexes. When the height standards derived from German patients are compared to those of a large multinational cohort of patients, 78% of whom were not confirmed by genetic testing, only minor differences in the height centiles become apparent. The population background therefore does not appear to play a major role for the observed differences. In a marked proportion of patients a decreased sitting height/height ratio is found. This was usually associated with scoliosis. Weight standards from our study group show that after 14 y of age German girls with PWS are heavier than their American counterparts. Standards for the body mass index of German patients of both sexes are increased over normal reference standards (p < 0.0001) and do increase with age (boys: p = 0.0038; girls: p = 0.0004). PWS genotypes or sex had no apparent influence on SDS for height, weight and body mass index. Conclusions: Because of the observed differences to other growth standards, use of the newly constructed centile curves is advocated in German patients with molecularly confirmed PWS to avoid delay in the diagnosis of additional growth-compromising conditions.     

Le syndrome de Prader-Willi : à propos d'un cas au Burkina Faso

A male infant was born at term after a normal pregnancy, without any evidence of prenatal asphyxia. On neonatal examination hypotonia was noticed, as well as on excessive weight at one month of age. The diagnosis of Prader-Willi syndrome was given and reinforced by the clinical evolution of the child's condition with time: persistant hypotonia, cryptorchidism, small penis and retardation of bone growth. A cranio-encephalic scan and transfontanel echography were normal at three months of age. The diagnosis was confirmed by analysis of the chromosomes, which showed a male karyotype with a microdélétion on chromosome 15 (q11.2q11.2).     

甲基化特异性PCR方法诊断Prader-Willi综合征

目的：Prader-Willi综合征(PWS)是多系统异常的复杂临床综合征, 仅根据临床症状很难诊断,国外已建立快速、高效、特异性、敏感性均佳的甲基化特异性PCR (MS-PCR)方法用于临床诊断,但我国还未有系统的对照研究。该研究目的便是建立 PWS的MS-PCR诊断方法,并对临床疑似患者进行筛查。方法：将44例受试者,分为正常对照组（16例）、临床确诊患者组（7例）及临床疑似患者组（21例）。采用盐析法提取基因组DNA;应用CpGemoneTM Fast Modification 试剂盒行亚硫酸盐修饰;以正常人为阴性对照,未修饰的基因组DNA为系统对照,以M（母源）、P（父源）两对引物同时对修饰产物行PCR;扩增产物以琼脂糖凝胶电泳分离。结果：①16例正常对照的PCR结果同时显示M,P两条带,7例临床确诊的PWS患者均只显示一条M带;②经MS-PCR筛查的21例临床疑似患者,2例确诊为PWS,其他19例排除PWS。结论：该研究成功建立MS-PCR,并对疑似患者进行了筛查确诊。MS-PCR为特异高效的PWS确诊方法且方便易行。     

Molecular analysis in Prader-Willi syndrome diagnosis

Prader-Willi syndrome is a rare neurogenetic disorder, which is evidence of genomic imprinting in undercentromeric region of chromosome 15. Defects of the SNRPN gene are the main cause of the syndrome. PWS is an incurable disorder. Nevertheless a diagnosis based on DNA analysis is possible. Molecular diagnostic research includes DNA methylation analysis in the 15q11-q13 region, the gene dosage analysis of the SNRPN gene and the microsatellite polymorphism analysis. The result of DNA analysis is the base of verification of the clinical diagnosis. It also enables to determine the type of molecular defect, from which a genetic risk is depended and what is the base of genetic counselling.     

Small nuclear ribonucleoprotein polypeptide N quantitative methylation analysis in infants with central hypotonia

Central hypotonic is one of the most difficult issues in neurology, ruling out neurogenetic syndromic causes is critical, Prader-Willi syndrome (PWS) it is the most frequent genetic syndrome, it is caused by the loss of expression of the paternal allele in a group of imprinted genes within 15q11-q13, and is characterized by severe prenatal and postnatal hypotonia. SNURF-SNRPN gene methylation detects 99% of the cases but fluorescent in situ hybridization (FISH) analysis is necessary to confirm chromosome microdeletions. The advantage of SNRP-quantitative strategy of methylated alleles is that it makes it possible to make the diagnosis and identify deletions and mosaicism in one reaction. In infants clinical diagnosis is difficult. It has been proposed that around 40% of hypotonic patients have PWS but an accurate percentage has not been established. Twenty-four central hypotonic infants were studied by this molecular strategy, showing 41.5% with the disease. This molecular approach also permitted calculation of gene dosage and detection of those cases with microdeletion.     

Glucose homeostasis in Prader-Willi syndrome and potential implications of growth hormone therapy

Diabetes mellitus is becoming a more frequently recognized complication of Prader-Willi syndrome. It has been reported that as many as 7-20% of individuals with Prader-Willi syndrome may develop this complication. Diabetes mellitus adds to the complexity of an already complex treatment program, causes many serious complications that greatly affect the quality of life of these individuals, and can lead to serious morbidity and mortality. Recent studies suggest that growth hormone (GH) might offer significant advantages to individuals with Prader-Willi syndrome. However, as a known diabetogenic agent, GH might also increase the propensity to develop diabetes mellitus. For this reason, the characteristics of the diabetes mellitus that develops in individuals with Prader-Willi syndrome must be studied and fully understood. The initial assumption has been that the diabetes mellitus associated with this syndrome is identical to that seen in obese individuals without Prader-Willi syndrome, in whom genetic factors and obesity lead to insulin resistance. Severe insulin resistance in turn leads to pancreatic failure and hence the symptom complex of type 2 diabetes mellitus. To determine if this same pattern is present in patients with Prader-Willi syndrome, we evaluated both obese children and adults with the syndrome. These patients were compared with obese individuals without Prader-Willi syndrome matched for age, gender and weight and who had not yet developed diabetes but had equally longstanding obesity. We compared the glucose and insulin responses of these two groups, using both oral and intravenous glucose challenges. The results demonstrated that individuals with Prader-Willi syndrome do not show the predicted insulin resistance that is seen in obese children without the syndrome. In fact, the individuals with Prader-Willi syndrome showed normal or increased insulin sensitivity. These data do not support the hypothesis that the high incidence of diabetes mellitus in patients with Prader-Willi syndrome is simply the result of obesity and therefore suggest a different aetiology.     

Prader-Willi综合征Ⅰ型和Ⅱ型缺失新生儿表型分析

目的 分析Prader-Willi综合征（PWS）父源性Ⅰ型、Ⅱ型缺失新生儿的表型差异。方法 纳入在复旦大学附属儿科医院临床诊断为PWS的新生儿,应用甲基化特异性多重连接探针扩增技术（MS-MLPA）和SNP芯片检测方法行PWS基因型分类,收集父源性Ⅰ型、Ⅱ型缺失患儿的临床表型资料,分析表型的差异。结果 13例PWS父源性缺失新生儿进入分析,其中MS-MLPA诊断10例,3例采用Affymetrix SNP芯片筛查诊断。Ⅰ型缺失5例,平均胎龄为36.2周,3例早产;Ⅱ型缺失8例,平均胎龄为38.9周,均为足月儿。Ⅰ型和Ⅱ型缺失各表型的发生率：肌张力低下和吸吮力差均为100%,特殊面容分别为80%和50%,色素减退分别为40%和37.5%,生殖系统异常分别为40%和87.5%。结论 肌张力低下和吸吮力差是PWS新生儿共同的临床特征,Ⅰ型缺失可能更易发生早产,特殊面容;Ⅱ型缺失生殖系统异常发生率较高,Ⅰ型缺失可能存在临床表型多样性。     

Neonatal hypotonia: don't forget the Prader-Willi syndrome

During the neonatal period the diagnosis of the Prader-Willi syndrome (PWS) is difficult because the syndrome is expressed mainly by severe hypotonia at this age and the typical clinical features of later life are not yet present. AIM: To identify all the PWS clinical markers in severe hypotonic newborns, which could facilitate an early diagnosis of the syndrome. METHODS: Twenty-one PWS newborns (14 males and 7 females) with severe hypotonia at birth were evaluated. Paediatricians skilled in syndromology carried out a careful clinical examination. Fluorescent in situ hybridization (FISH) analysis and/or a methylation test was used to confirm the PWS clinical diagnosis. RESULTS: The clinical diagnosis of PWS was reached at a mean age of 7.4 mo with genetic confirmation at 11 mo of life. In 12 newborns at least 3 craniofacial features were present (57%), suggesting the diagnosis of PWS. Two craniofacial dysmorphic characteristics were described in 6 newborns and only 1 in 3 cases. Cryptorchidism was monolateral in 6 and bilateral in 7 patients; in one newborn both testes were in scrotum. A micropenis was described in one patient and hypoplasia of the labia minora was reported in two females. CONCLUSIONS: Diagnosis by means of dysmorphologic evaluation is difficult in the neonatal period. The presence of severe hypotonia should always induce neonatologists to perform specific genetic tests in order to obtain an early diagnosis of PWS.     

新生儿Prader-Willi综合征13例临床表型分析

目的 分析Prader-Willi综合征（PWS）新生儿期的临床表现,为临床早期筛选及进一步行分子诊断提供帮助。方法 回顾性分析2009年8月至2011年8月在北京军区总医院附属八一儿童医院依据MS-PCR和MS-MLPA方法确诊为PWS患儿的诊断、分型和临床表型资料,分析中国PWS新生儿期典型特征。结果 13例PWS进入分析,男9例,女4例,确诊年龄4～28 d。足月儿10例,早产儿2例,过期产儿1例。孕母高龄9例（69.2%）,羊水污染8例（61.5%）,羊水过多3例（23.1%）,胎膜早破5例（38.5%）,异常胎位4例（30.8%）,宫内窘迫9例（69.2%）。 9例为父源性15q11.2-q13区域缺失致病,4例为母源性同源二倍体。4例母源性同源二倍体患儿均可见中枢性肌张力低下和皮肤色素减退,吸吮缓慢2例(50.0%)、哭声微弱3例(75.0%)、男性隐睾1例(25.0%)、女性小阴唇3例(75.0%);均未见特殊面容和唾液黏稠,均不需特殊喂养。9例父源性15q11.2-q13区域缺失患儿均可见中枢性肌张力低下、皮肤色素减退和哭声微弱,吸吮缓慢2例(22.2%)、需特殊喂养7例(77.8%)、特殊面容5例(55.6%)、男性隐睾7例(77.8%)、阴茎短小4例（44.4%）、女性小阴唇1例(11.1%)、唾液黏稠5例(55.6%)。结论 母源性同源二倍体患儿的特殊面容和男性生殖器发育不全的发生率低于父源性15q11.2-q13区域缺失患儿。新生儿期皮肤色素减退及中枢性肌张力低下是中国PWS新生儿普遍存在的特征,可作为进一步行PWS分子诊断的初步筛选指标。     

Cytogenetic detection of Prader-Willi syndrome in infancy

In the case of characteristic chromosomal deletion of chromosome 15(q11----q13) the diagnosis of the Prader-Willi syndrome can be already confirmed in early infancy as shown in our case report. In this connection cytogenetic high-resolution techniques are indispensable. Cytogenetic and clinical problems are discussed.     

Body composition in Prader-Willi syndrome: assessment and effects of growth hormone administration

Children and adults with Prader-Willi syndrome are usually overweight, if not obese. Nevertheless, it is now thought that the body composition exhibited by such individuals is markedly dissimilar to that found in simple obesity. In fact, the body composition typical of Prader-Willi syndrome is actually more characteristic of that found in individuals with growth hormone (GH) deficiency, namely an increased level of adiposity in the limbs in comparison with the trunk and an overall reduction in fat-free mass. This variation in body composition may impact upon the assumptions inherent in many techniques used to measure body size and body composition, such as the use of body mass index and skinfolds. Therefore, it is important that the potential error in body composition assessment is understood by professionals evaluating patients with Prader-Willi syndrome. Accurate assessment of body composition is critical in Prader-Willi syndrome, as a number of recent studies have revealed extremely similar findings relating to the effect of exogenous GH on the body composition of patients with this syndrome. Other notable findings of these studies include significant increases in muscle strength and exercise capacity, which probably result from the changes in body composition. The routine use of exsogenous GH to treat this extremely debilitating syndrome should now be considered.     

Body composition in Prader-Willi syndrome: assessment and effects of growth hormone administration

Children and adults with Prader-Willi syndrome are usually overweight, if not obese. Nevertheless, it is now thought that the body composition exhibited by such individuals is markedly dissimilar to that found in simple obesity. In fact, the body composition typical of Prader-Willi syndrome is actually more characteristic of that found in individuals with growth hormone (GH) deficiency, namely an increased level of adiposity in the limbs in comparison with the trunk and an overall reduction in fat-free mass. This variation in body composition may impact upon the assumptions inherent in many techniques used to measure body size and body composition, such as the use of body mass index and skinfolds. Therefore, it is important that the potential error in body composition assessment is understood by professionals evaluating patients with Prader-Willi syndrome. Accurate assessment of body composition is critical in Prader-Willi syndrome, as a number of recent studies have revealed extremely similar findings relating to the effect of exogenous GH on the body composition of patients with this syndrome. Other notable findings of these studies include significant increases in muscle strength and exercise capacity, which probably result from the changes in body composition. The routine use of exogenous GH to treat this extremely debilitating syndrome should now be considered.