NSD1 mutations generate a genome-wide DNA methylation signature.

Sotos syndrome (SS) represents an important human model system for the study of epigenetic regulation; it is an overgrowth/intellectual disability syndrome caused by mutations in a histone methyltransferase, NSD1. As layered epigenetic modifications are often interdependent, we propose that pathogenic NSD1 mutations have a genome-wide impact on the most stable epigenetic mark, DNA methylation (DNAm). By interrogating DNAm in SS patients, we identify a genome-wide, highly significant NSD1(+/-)-specific signature that differentiates pathogenic NSD1 mutations from controls, benign NSD1 variants and the clinically overlapping Weaver syndrome. Validation studies of independent cohorts of SS and controls assigned 100% of these samples correctly. This highly specific and sensitive NSD1(+/-) signature encompasses genes that function in cellular morphogenesis and neuronal differentiation, reflecting cardinal features of the SS phenotype. The identification of SS-specific genome-wide DNAm alterations will facilitate both the elucidation of the molecular pathophysiology of SS and the development of improved diagnostic testing.

Ambiguous genitalia, impaired steroidogenesis, and Antley-Bixler syndrome in a patient with P450 oxidoreductase deficiency.

Cytochrome P450 oxidoreductase deficiency is a recently established autosomal recessive disease characterised by ambiguous genitalia, impaired steroidogenesis, and skeletal malformations, referred to as Antley-Bixler syndrome. Clinical manifestations in affected patients are highly variable. We report on a girl with P450 oxidoreductase deficiency who presented with virilisation at birth. There was transient maternal virilisation during pregnancy as well. She was initially diagnosed with congenital adrenal hyperplasia caused by 21-hydroxylase deficiency and/or aromatase deficiency. At 1 year of age, skeletal abnormalities suggestive of Antley-Bixler syndrome were detected. Molecular analysis of the fibroblast growth factor receptor 2 (FGFR2) gene was normal but POR gene analysis showed that she was homozygous for an R457H missense mutation. The diagnosis, P450 oxidoreductase deficiency, was confirmed. Results of her endocrine studies and urinary steroid profiling are also presented.

Severe neonatal manifestations of Costello syndrome.

BACKGROUND: Costello syndrome (CS) is due to mutations in HRAS, with the most common mutation being c.34G>A (p.G12S), found in most patients in all the published series. A small number of less common mutations have been reported. POPULATION STUDIED: HRAS mutation analysis has been undertaken in 74 predominantly British patients with a possible diagnosis of CS. A HRAS mutation was found in 27 patients, 15 of whom have been previously reported. PHENOTYPE ANALYSIS: Four cases had an unusually severe phenotype, associated in three cases with two unusual mutations, c.35G>A, p.G12D in two cases and c.34G>T, p.G12C in the other. Hypoglycaemia, renal abnormalities, severe early cardiomyopathy, congenital lung and airway abnormalities, pleural and pericardial effusion, chylous ascites and pulmonary lymphangectasia are confirmed as part of the clinical spectrum seen in CS. A lung pathology resembling alveolar capillary dysplasia is reported in one case. CONCLUSION: These cases illustrate that the diagnosis of CS may be difficult in the newborn period, and should be considered in the differential diagnosis of the sick newborn infant with multisystem disease. Study of more cases will be required to establish if there is a definite association between severe disease and less common mutations.

Chromosomal abnormalities and FMR1 gene premutation in Chinese women with premature menopause.

OBJECTIVE: To study the prevalence of chromosomal abnormalities and FMR1 gene premutation in Chinese women with premature menopause in Hong Kong. DESIGN: Retrospective study. SETTING: Clinical Genetic Service, Hong Kong. PARTICIPANTS: Chinese women with premature menopause referred for cytogenetic study from January 1983 to November 2003. MAIN OUTCOME MEASURES: Chromosomal abnormalities, FMR1 gene premutation. RESULTS: Chromosomal abnormalities were present in 15.6% of Chinese women who suffered premature menopause. X-chromosome abnormality was involved in over 80% of cases. FMR1 gene premutation was present in 0.86% of 116 cases screened for this abnormality. The predominance of X-chromosome abnormality accounted for the shorter stature, younger menopausal age, and higher prevalence of dysmorphic features among the cytogenetically abnormal patients. However, on logistic regression, no clinical feature was significantly correlated with cytogenetic abnormality. CONCLUSIONS: The prevalence of chromosomal abnormalities among Hong Kong Chinese women who suffer premature menopause was comparable with that of Caucasian and Chinese populations elsewhere. Because clinical features are poor predictors of cytogenetic abnormality, a pragmatic approach to screening is advocated. The carrier rate of fragile X premutation in these women appeared lower than that of Caucasians. Nevertheless, a search for FMR1 gene premutation, in addition to conventional chromosomal study, has important implication for prenatal diagnosis and fertility management for the extended family.

Cytogenetic analysis of patients with primary and secondary amenorrhoea in Hong Kong: retrospective study.

OBJECTIVE: To estimate the incidence and type of chromosomal abnormalities in patients with primary and secondary amenorrhoea in Hong Kong. DESIGN: Cytogenetic analysis and retrospective review. SETTING: Clinical Genetic Service, Department of Health, Hong Kong. PATIENTS: Case records of 549 patients with either primary (n=237) or secondary (n=312) amenorrhoea referred to the Clinical Genetic Service from 1 January 1991 to 30 April 2002 were reviewed. All these patients with amenorrhoea would have karyotyping (G banding) performed. MAIN OUTCOME MEASURES: Clinical characteristics of patients, and incidence and type of chromosomal abnormalities in the local population. RESULTS: Sex chromosome anomaly was found in 24.5% and 9.9%, respectively, of women with primary and secondary amenorrhoea. In those with primary amenorrhoea, male karyotype was identified in 8.4% and X-chromosome abnormalities in 16.0%. CONCLUSION: The incidence of chromosomal abnormalities in women with amenorrhoea is similar to that reported in the literature. Chromosomal abnormalities are identified often enough to warrant karyotyping of all women with amenorrhoea.

Williams-Beuren syndrome in the Hong Kong Chinese population: retrospective study.

OBJECTIVE: To estimate the incidence and document the clinical characteristics of Williams-Beuren syndrome in the Hong Kong Chinese population. DESIGN: Cytogenetic analysis and retrospective study. SETTING: Clinical Genetic Service, Department of Health, Hong Kong. PATIENTS: Forty-one Chinese patients with Williams-Beuren syndrome. MAIN OUTCOME MEASURES: From 1 January 1995 to 30 June 2002, fluorescence in situ hybridisation was used to confirm diagnoses in 41 cases of Williams-Beuren syndrome by detecting chromosome 7q microdeletion. Case records were reviewed, the incidence of the condition in the local population was estimated, and the main clinical characteristics were determined. RESULTS: The minimal incidence of Williams-Beuren syndrome in this locality was estimated to be approximately 1 per 23500 live births. Common dysmorphic facial features included periorbital fullness (83%), full lips (80%), a long philtrum (51%), a flat nasal bridge (41%), and abnormal teeth (37%). No patients had a stellate iris. The majority (82%) had at least one documented cardiac anomaly; among these patients, peripheral pulmonary stenosis was diagnosed in 61% and supravalvular aortic stenosis in 45%. Nearly all (93%) of the study group exhibited developmental delay. CONCLUSION: As in the West, patients with Williams-Beuren syndrome in the Hong Kong Chinese population display craniofacial dysmorphism, cardiovascular anomalies, and mental deficiency. Supravalvular aortic stenosis-the cardiac defect most commonly associated with Williams-Beuren syndrome in western countries-is less common than peripheral pulmonary stenosis in this region. Studies involving periodic cardiovascular evaluation are needed to confirm if this difference is significant.

Dentatorubral-pallidoluysian atrophy in two Chinese families in Hong Kong.

We report on two Hong Kong Chinese families with dentatorubral-pallidoluysian atrophy. Two children in one family presented with progressive myoclonic epilepsy syndrome, and two children in the other family presented with ataxochoreo-athetoid symptoms. Early-onset childhood dentatorubral-pallidoluysian atrophy involved mental retardation, whereas myoclonic epilepsy was the predominant complaint in later-onset childhood version of the disease. Aspiration pneumonia was common in the late stage of disease. Dentatorubral-pallidoluysian atrophy is an autosomal dominant condition attributed to CAG trinucleotide repeats in the dentatorubral-pallidoluysian atrophy gene. The four children in this series had 63 to 79 CAG repeats. The expanded allele was inherited from the father in both families. One father had 54 CAG repeats and was asymptomatic; the other had 66 repeats and had an unsteady gait. Because the radiological, electroencephalographic, and electrophysiological findings were non-specific, we suggest that DRPLA gene testing should be performed in any child presenting with a variable combination of myoclonic epilepsy, mental retardation or developmental regression, and ataxochoreo-athetosis.

Neonatal screening in Hong Kong and Macau.

For the implementation of the neonatal screening program, the following factors have to be considered for the selection of conditions to be screened and evaluation of outcome. These include the factors pertaining to public health impact, availability and acceptability of the screening system, and other social issues involved in the implementation. In the context of Hong Kong, Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency and Congenital Hypothyroidism (CHT) have been highlighted in the early 1980s for consideration. A territory wide program for screening these conditions was started in 1984. Since then, over 99% of all newborns in Hong Kong was screened. Of these, around 70% were delivered in public hospitals, and the remaining were from private hospitals. Pre-screening education was emphasized, and 95% of pregnant ladies received information about this screening program from the Maternity and Child Health Centers run by the Department of Health, Hong Kong. For those who were born in public hospitals, the incidence of CHT was 1 in 2404 (269/646,580), while that of G6PD deficiency was 4.5% in male newborns and 0.3% in female newborns. This paper highlights details of the screening program, including its outcome evaluation. In Macau, CHT screening has not been started. Instead, G6PD deficiency screening commenced in 1977 in one of the two major hospitals where most newborns are delivered. Methodology and results of this program are presented.