Using genetic epidemiology to study Rett syndrome: the design of a case-control study

Impacts of national surveillance for uncommon conditions in childhood

The Australian Paediatric Surveillance Unit (APSU) facilitates the conduct of national collaborative research that is consistent with national health priorities, has potential to impact on public health, and addresses gaps in knowledge. Since 1993 paediatricians and other child health specialists have contributed monthly data on rare childhood conditions to the APSU. Over 40 conditions, including infectious diseases, injuries, vaccine-preventable diseases and genetic disorders have been studied. Information on epidemiology, frequency, diagnosis, management and short-term outcomes of these conditions is collected and provides evidence to support changes to clinical practice, prevention policy and allocation of health resources. In this review we give examples of the value of information gathered through the APSU surveillance system in the last 14 years.

Beyond counting cases: public health impacts of national Paediatric Surveillance Units

Paediatric Surveillance Units (PSUs) have been established in 14 countries and facilitate national, prospective, active surveillance for a range of conditions, with monthly reporting by child health specialists. The International Network of Paediatric Surveillance Units (INoPSU) was established in 1998 and facilitates international collaboration among member PSUs and allows for sharing of resources, simultaneous data collection and hence comparison of data from different geographical regions. The impact of data collected by PSUs, both individually and collectively as members of INoPSU, on public health outcomes, clinical care and research is described.

The epidemiology of mental retardation: challenges and opportunities in the new millennium

There are a number of problems and challenges in relating the science of epidemiology to mental retardation (MR). These relate to how MR is defined and classified and how these definitions may change over time. These as well as other differences in ascertainment sources and methods need to be considered when comparing MR prevalence over time and place. On the other hand, advances in technology also provide new and efficient methods of data collection both by data linkage and by use of web-based methods to study rare diseases. While prevalence studies have not been individually reviewed, we have examined the range of data including recent studies relating to how prevalence differs according to age, gender, social class and ethnicity. Some problems with available etiological classification systems have been identified. Recent etiological studies, most of which use different classification systems, have been reviewed and explanations have been postulated to account for differences in results. Individual risk factors for MR are considered whilst the option of considering a population as opposed to a high risk strategy to MR prevention is raised. This might well involve improving the social milieu surrounding the occurrence of individual risk factors. The impact of biotechnological advances such as antenatal and neonatal screening and assisted reproduction on MR are discussed. The issue of how inequalities in access to technology may impact on case identification and even have the potential to further widen inequalities is raised. The importance of extending the use of epidemiological tools to study the social, health and economic burden of MR is also emphasized. However, in order to apply to MR the "prevention-intervention-research" cycle, which surely underpins all epidemiology, it is vital to ensure that the methodological challenges we raise are adequately addressed.

Genetics of Rett syndrome: properties of the newly discovered gene and pathobiology of the disorder

The recent identification of mutations in the gene methyl-Cpg-binding protein-2 (MECP2) in girls with Rett syndrome (RS) has firmly established the molecular genetic basis of this unique, X-linked, dominant disorder and provides a dramatic conclusion to an intensive, decade-long search. This finding has ramifications far beyond establishing the gene for RS. Recent data indicate that the clinical phenotypes for MECP2 mutations range from mild disability in the mother of a girl with RS to rapidly progressive encephalopathy in her brother. Further, the pathobiology of MECP2 could be a prototype for other disorders of neurodevelopment. MECP2 encodes a methyl-CpG-binding protein (MeCP2), which is critical for transcriptional silencing of an as yet unknown number and type of genes responsible for the pathobiology of RS. As such, this discovery opens up completely new vistas as to fundamental neurobiologic processes, to disease mechanisms in the neurodevelopmental disabilities, and to potential new therapeutic strategies for RS and related disorders.

Family data in Rett syndrome: association with other genetic disorders

BACKGROUND

Rett syndrome is a neurological disorder, almost exclusively affecting girls.

METHODOLOGY

Between 1993 and 1995 pedigree data were obtained from families of girls registered with the Australian Rett syndrome database.

RESULTS

Although 21 individual disorders were reported to be present in family members of affected girls, there was no apparent clustering of the same disorder in different families. However it was certain that a geneticist had been involved in only 10.9% of cases.

CONCLUSIONS

Mutations in the MECP2 gene have now been reported in a proportion of sporadic cases. Thus, it will be important to examine this phenotype-genotype correlation in the Australian cohort. Where a mutation is found, prenatal diagnosis in a subsequent pregnancy will be a possibility. Using the Australian population database and in conjunction with the clinical genetic services in each state it is planned to contact families with an affected girl to offer testing and counselling.