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Prader-Willi syndrome (PWS) is a neurogenetic disorder associated with recurrent genomic recombination involving low copy repeats (LCRs) located in the human chromosome 15q11-q13. Previous studies of PWS patients from Asia suggested that there is a higher incidence of deletion and lower incidence of maternal uniparental disomy (mUPD) compared to that of Western populations. In this report, we present genetic etiology of 28 PWS patients from Taiwan. Consistent with the genetic etiology findings from Western populations, the type II deletion appears to be the most common deletion subtype. Furthermore, the ratio of the two most common deletion subtypes and the ratio of the maternal heterodisomy to isodisomy cases observed from this study are in agreement with previous findings from Western populations. In addition, we identified and further mapped the deletion breakpoints in two patients with atypical deletions using array CGH (comparative genomic hybridization). Despite the relatively small numbers of patients in each subgroup, our findings suggest that the genomic architecture responsible for the recurrent recombination in PWS is conserved in Taiwanese of the Han Chinese heritage and Western populations, thereby predisposing chromosome 15q11-q13 to a similar risk of rearrangements. [ABSTRACT FROM AUTHOR]

Aim: Several different genetic defects have been found to result in the characteristic phenotypic expression of Prader–Willi syndrome (PWS). Methods: We performed a retrospective analysis of 67 cases of molecularly confirmed PWS diagnosed from January 1980 through July 2006 in five medical centres in Taiwan. Clinical manifestations were compared between patients with deletion and those with maternal uniparental disomy (UPD). Results: Deletion was present in 56 (84%), UPD in 10 (15%), and a probable imprinting centre deletion or imprinting defect in 1 (1%). PWS with deletion was more likely than that with UPD to be characterized by hypogonadism (p < 0.001), small hands and feet (p < 0.001), and hypopigmentation (p < 0.002). Both maternal (p = 0.015) and paternal age (p = 0.021) were higher in the UPD group. No other clinical features differed significantly different between the two groups. Conclusion: In contrast to most Western populations with a higher incidence of UPD, this study of PWS in Taiwan shows a higher incidence of deletion. There may be subtle phenotypic differences between the UPD and deletion genotypes, but its not clear that these are important clinically. [ABSTRACT FROM AUTHOR]

Background: Prader–Willi syndrome (PWS) is a congenital disorder caused by absent expression of paternal genes in 15q11-13 affecting multiple systems. The information concerning the clinical features of this genetic disorder is incomplete in Taiwan. Methods: A retrospective analysis was carried out of 70 PWS patients (39 male, 31 females; age range, 1 month–22 years) seen in four major medical centers in Taiwan from January 1980 through June 2005. All cases were confirmed by methylation-specific polymerase chain reaction. The molecular characteristics, birth history, clinical presentation and laboratory studies were analyzed. Results: Complete genetic analysis was performed in 52 of the 70 patients with PWS. The abnormalities found included deletions in 45 (87%), maternal uniparental disomy (UPD) in five (10%), and a probable imprinting center deletion or an imprinting defect in two (4%). The average weight of the patients at birth was 2588 ± 540 g. Bone age delay of >2 years and growth hormone (GH) deficiency were noted in 11/40 (28%) and 12/20 (60%), respectively. In the 18 in whom both bone age and GH were assessed, abnormalities of both were found in two (11%). In 2000, Taiwan instituted the Rare Diseases and Orphan Drugs Act and mandated a three-phase screening protocol for PWS. Of the 41 patients diagnosed with PWS before 2000, only four (10%) were diagnosed before the age of 3 months; in the 29 patients diagnosed after 2000, in 15 (52%) the syndrome was confirmed before 3 months of age ( P < 0.001). Conclusions: The present finding is in contrast to that of most previous reports that indicated a higher incidence of UPD in PWS. It is unclear whether this discrepancy in the incidence of UPD arises from under-diagnosis or because of ethnic differences, a question worthy of further study. The three-phase screening protocol has generated notable improvement in the early diagnosis of PWS in Taiwan. [ABSTRACT FROM AUTHOR]

Unlabelled: Recent molecular cytogenetic studies have elucidated the origin and nature of extra structurally abnormal chromosomes (ESACs) or small supernumerary chromosomes, which are often associated with developmental delay and malformations. We studied the prevalence of inv dup(15) in a nationwide screening programme for mentally retarded children in Taiwan and tried to correlate the genotype and phenotype in those patients. Fluorescence in situ hybridization (FISH) analysis using D15Z, D15Z1, and the cosmids from the Prader-Willi/Angelman syndrome chromosome region (PW/ASCR) was performed on 54 patients (0.45%) with ESACs from 11893 probands within a 5-year period. Of them, inv dup(15) was confirmed in 25 children (46.3%) by FISH analysis. The PW/ASCR probes were used to clarify the size and DNA composition of the markers. Patients with inv dup(15) chromosomes, containing only the heterochromatin or little euchromatin of the proximal 15q (i.e., pter-->q11:q11-->pter) may have a rather mild or nearly normal phenotype (group 1). Only one patient had some features suggestive of Angelman syndrome, but was considered to be a result of deleted (15)(q12) in the chromosome 15 homologue. Additional copies within D15S11 through GABRB3 (15q11.2-13) resulted in an abnormal phenotype which involved mental and developmental delay but was different from the classical phenotype of PW/AS (groups 2, 3). Signs of autistic behavior did occur in each group. FISH combined with microsatellite analyses showed that the marker was often of maternal origin in de novo cases (n = 12, 86%), or inherited from the mother in only one familial case. Down-inv dup(15) was mentioned in two cases. Unusual features including diaphragmatic eventration, hyperlaxity of joints, arachnodactyly, brain atrophy, epilepsy (particularly infantile spasm), ataxia, genital abnormalities, and cleft lip/palate were noted in those patients. This observation expands the range of phenotypic expression associated with this relatively common ESAC.Conclusion: Marked phenotypic diversities exist in children with inv dup(15), dependent upon the size or genetic composition of the markers, degree of mosaicism, parental origin and familial occurrence or not. Patients with a larger inv dup(15) marker chromosome including the PW/ASCR may have a higher risk of abnormalities, but not the typical Prade-Willi/Angelman syndrome phenotype. [ABSTRACT FROM AUTHOR]

Prader-Willi syndrome (PWS) is a genetic disorder with obesity, developmental delay, short stature, and behavioral abnormalities. The study aimed to assess the functional independence in children with PWS. The Functional Independence Measure for Children (WeeFIM) was used to evaluate 81 children with PWS (44 boys and 37 girls) with a median age of 11 years 1 month (range 2 years 8 months to 20 years 2 months) were recruited between January 2013 and December 2016. The mean total WeeFIM score was 103.8 (maximum 126). Sixty-five patients (80%) had deletion type PWS, 16 (20.0%) had nondeletion type. The scores were 103.6 ± 18.5 for deletion and 104.8 ± 18.3 for nondeletion type (p = .405), 104.8 ± 19.3 in boys and 102.6 ± 17.3 in girls (p = .293). The mean self-care, mobility, and cognition scores were 47 (maximum 56), 33 (maximum 35), and 24 (maximum 35), respectively. All total scores and 18 subscores in the three functional domains were positively correlated with age (p < .05). Most children required assistance in problem-solving, comprehension, and expression. The WeeFIM identified the strengths and limitations of children with PWS and confirmed that support and supervision were needed in cognitive and self-care tasks., (© 2018 Wiley Periodicals, Inc.)

Objective: To identify Prader-Willi syndrome (PWS) and Angelman syndrome (AS) among fetuses with suspicious deletion of the chromosomal region 15q11-q13., Methods: In a retrospective study, data were assessed from fetuses missing chromosomal band 15q12 that underwent molecular diagnosis at the National Chen-Kung University Hospital, Tainan, Taiwan, between January 2001 and December 2012. Amniocytes were subjected to molecular testing, including fluorescence in situ hybridization (FISH) analysis, methylation-specific PCR (M-PCR), and methylation-specific multiplex-ligation-dependent probe amplification (MS-MLPA)., Results: During the 12-year study period, 26 041 amniocyte samples were analyzed at the study center and 27 (0.1%) were found to have a missing 15q12 band. A further 16 samples with a missing 15q12 band were received from other cytogenetic laboratories; as a result, 43 amniocyte samples lacking chromosomal band 15q12 underwent further molecular testing. Among these samples, 3 fetuses (7.0%) were found to have PWS (n=1) or AS (n=2)., Conclusion: A minority of cases with missing 15q12 had deletion of the PWS/AS critical region. This finding draws attention to the subtle structural rearrangements that occur on 15q11-q13 and provides useful information for prenatal diagnosis of PWS and AS., (Copyright © 2013 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.)