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Leslie Ordal, MSc. in Genetic Counselling, candidate, Clinical Genetics Department, Hospital for Sick Kids, Toronto, ON Feature Carrier Screening G enetic diseases can occur among people of all backgrounds, but some genetic disorders occur more frequently in certain ethnic groups. Screening is offered to individuals or couples on the basis of their ethnic background to see if they are at a higher risk of having a child with one of these genetic conditions. Some conditions screened for are more common and have available treatments, such as sickle cell disease, while others are rare enough to fall into the category of orphan diseases. In Ontario, screening for several orphan diseases is offered to individuals of Ashkenazi Jewish heritage. The conditions selected for screening are either more likely to occur in this population or there is a common mutation in this group that is easily tested. The orphan diseases currently covered are Tay-Sachs disease, Canavan disease, mucolipidosis (type IV), familial dysautonomia, Niemann-Pick disease (types A and B), Bloom syndrome, and Fanconi anemia (group C). Humans have about 30,000 genes, which act as instructions to tell the body how to grow and function. Everyone has two copies of each gene - one copy is inherited from each parent. If a gene has a mutation (a change that causes it not to work properly), this can result in a medical condition. The conditions targeted by ethnicity-based carrier screening are recessive, meaning there must be mutations in both copies of a gene to cause the disease. A person with a mutation in only one copy is called a carrier, meaning they do not show symptoms of the disease but can pass the mutation on to their children. Everyone is a carrier of an estimated 6-10 recessive conditions, but this does not typically pose a risk to their health. If, however, two parents carry a mutation in the same gene, there is a 25% chance for each child to inherit both mutations and therefore have the genetic condition. Ethnicity-based carrier screening aims to identify couples at a higher risk of carrying the same genetic condition due to being members of the same ethnic group. They can then be offered information and additional testing to help make the family planning decisions that are right for them. Carrier screening is often ADVOCATE, Volume 20/Issue 2 Summer 2013 offered in the context of prenatal care, but it is ideally done pre-conception. Annual screening clinics, such as those at Mount Sinai Hospital in Toronto, for example, exist to raise awareness and give people with Ashkenazi Jewish heritage the chance to be screened at any point during their reproductive life. For an individual who is found to be a carrier of a recessive genetic condition, testing is offered to their partner. If both partners are found to be carriers of the same condition, they are usually referred for genetic counselling to receive support and learn more about their options, which may vary depending on whether they are currently pregnant. One option is to have no additional testing. Another option is prenatal diagnosis, where chorionic villus sampling (CVS) or amniocentesis is used to see if the fetus is affected with the genetic support about their new child’s medical needs. Unfortunately, as with most orphan diseases, highly effective treatments are not yet available for the orphan diseases targeted through ethnicity-based carrier screening in Ontario. Treatments for this group of diseases are largely supportive and symptom-based. Tay-Sachs disease causes progressive damage to the nervous system, often beginning with seizures and loss of motor control and eventually leading to difficulties in swallowing and breathing. Most affected children do not live past the age of four. Canavan disease is also characterized by neurodegeneration that begins in infancy, with life expectancy varying from childhood to the early 20’s. Mucolipidosis (type IV) is caused by the abnormal accumulation of lipids in the lysosomes, leading to vision problems, progressive loss of motor control, and intellectual disability. Familial dysauto- The conditions targeted by ethnicity-based carrier screening are recessive, meaning there must be mutations in both copies of a gene to cause the disease. condition in question. These tests provide high diagnostic accuracy but come with an increased risk of miscarriage. Parents of an affected fetus have the option to continue or end the pregnancy. This is a highly personal and often difficult decision, but families are supported in whatever choice they make. Another option is preimplantation genetic diagnosis, or PGD, which uses in vitro fertilization (IVF) technology to create embryos that are tested for the genetic condition before implantation. PGD is not covered by OHIP and is therefore less commonly used than prenatal diagnosis methods. Additionally, issues such as what to do with affected and other non-implanted embryos - which may be stored indefinitely, discarded, donated to others experiencing infertility, or used for research purposes - may have an impact on some families’ decision to use PGD technology. Parents who choose to continue an affected pregnancy are given guidance and nomia affects the development and survival of certain nerves. Symptoms such as impaired blood pressure and body temperature regulation may be present at birth, with poor motor control and developmental delay also often occurring. Niemann-Pick disease type A presents in infancy with spleen and liver problems and rapid neurogeneration, with a life span of around 3 years. Niemann-Pick type B is typically milder and more variable in its symptoms; affected individuals may live into adulthood. Bloom syndrome causes problems with growth, an increased susceptibility to certain infections, and a higher risk of developing cancer. Fanconi anemia can also cause immunodeficiency and a higher cancer risk, along with additional health problems. In some places, such as in some areas of the U.S., carrier screening for multiple orphan diseases – as well as more common Continued on page 6 5 Robert Scheuermann, MLT, BSc., MBA/HCM Getting To Know District 6 High quality laboratory services D istrict 6 spans a collection of 9 counties and/or regional municipalities in Southwestern Ontario, which includes Wentworth, Brant, Halton, Waterloo, Perth, Wellington, Dufferin, Grey, and Bruce counties. These areas are beautiful with some breathtaking views extending along the Niagara escarpment through Hamilton to the tip of the Bruce Peninsula. More than 2 million people reside in the 20,000 km2 expanse that makes up the areas of District 6. There are many great laboratory minds and leaders within the boundaries of District 6. The laboratory services therein range from small rural health labs to moderately-sized healthcare facilities to state of the art, internationally-recognized, academic centres of excellence. countryside a few short hours from Toronto and the U.S. – a destination internationally renowned as one of North America’s great arts towns.” (http://www.visitstratford.ca/) To the southeast is the city of Brantford, which is well known to be the Canadian home of Alexander Graham Bell and Wayne Gretzky. Moreover, the Brantford Community Healthcare System (BCHS), a leader in healthcare and laboratory technology, became the home of “Canada’s first automated laboratory” in 2011. “This is the first time chemistry, immunochemistry, hematology and coagulation have been automated into a single integrated system, said Don Manning, director of laboratory and diagnostic imaging. “It improves patient safety and it improves patient care because the tests needed for There is much world-renown testing and research being conducted at the Hamilton hospitals and McMaster University in the laboratory disciplines of genetics, chemistry, immunology, hematology, and pathology with exciting achievements. Stratford is the main laboratory services hub of the Inter-Hospital Laboratory Partnership (IHLP), a partnership of 12 rural/ community hospital laboratory services. Seven of the twelve IHLP medical laboratories are situated within District 6 and provide high quality laboratory services for a large geographical area. “Few places in Ontario are lovelier or more alive with culture and character than Stratford. We are a charming Victorian city nestled in pastoral diagnosis can be done much more quickly,” said Dr. Kathy Chorneyko, the laboratory’s medical director. “A faster test result means quicker diagnosis and treatment for the patient.” (http://www.brantfordexpositor.ca/2011/02/04/bgh-opens-canadasfirst-automated-laboratory) The home of the Hamilton Regional Laboratory Medicine Program (HRLMP) is less than thirty minutes down Highway 403 from Brantford in the City of Hamil- Feature continued from page 5 likely the result of both the recognition that many people have diverse ancestry and the rapidly falling cost of genetic testing in general. It will be interesting to see if similar changes take place in Ontario and else- conditions, such as sickle cell and other hemoglobinopathies – is increasingly being offered regardless of ethnicity. This is 6 ton. The HRLMP is a collaborative program of Hamilton Health Sciences Centre, St. Joseph’s Healthcare and McMaster University and is the main academic hub for laboratory medicine in District 6. There is much world-renown testing and research being conducted at the Hamilton hospitals and McMaster University in the laboratory disciplines of genetics, chemistry, immunology, hematology, and pathology with exciting achievements. “A team of scientists at McMaster University has discovered the drug, thioridazine, successfully kills cancer stem cells in the human while avoiding the toxic side-effects of conventional cancer treatments.” The unusual aspect of our finding is the way this human-ready drug actually kills cancer stem cells; by changing them into cells that are non-cancerous,” said Mick Bhatia, the principal investigator for the study and scientific director of McMaster’s Stem Cell and Cancer Research Institute (SCC-RI) in the Michael G. DeGroote School of Medicine. (http://fhs.mcmaster. ca/main/news/news_2012/targeting_human_cancer_stem_cells.html) There are many great laboratory professionals in the district that provide never-ending passion, knowledge, and experience to academic teaching centres, medical laboratory research and laboratory diagnostic support services to the benefit of more than 2 million Ontarians. This is just a fractional snapshot of the amazing work that laboratory professionals do in District 6 and throughout the Province of Ontario. ❖ where in Canada given the great advances taking place in genetic testing technology, as well as the increasing focus on, and awareness of, orphan diseases. ❖ ADVOCATE, Volume 20/Issue 2 Summer 2013