Five recessive diseases are common in the Charlevoix and Saguenay Lac-Saint-Jean (SLSJ) regions:
• Congenital lactic acidosis
• Hereditary sensitivomotor neuropathy
• Spastic recessive ataxia of Charlevoix-Saguenay
• Cystic fibrosis of the pancreas
Principle of inheritance of a recessive disease
To have a recessive disease, a person must inherit two copies of the abnormal gene.
A person whose cells include only one abnormal gene is a carrier but not affected by the disease. When two people with an abnormal disease gene want to have a child, there are three possibilities: 25% to have a non-affected child who is not a carrier, 50% to have a carrier (unaffected child), and 25% to have an affected child.
Frequency of carrier rate
The frequency of being a carrier is substantially the same for each of these diseases, ie about 1 in 20 individuals.
The detection rate is 93% to 99% among French Canadians. Currently, only people who already have a known case in their family or whose partner is a known carrier may be screened as part of the Canadian public health system. However, it is possible to pass genetic tests in Procrea Fertility in order to know its carrier status of these diseases.
affected at birth
in the population
|Congenital lactic acidosis||1/2000||1/23|
with or without agenesis of the
|Spastic recessive ataxia of |
|Cystic Fibrosis: (FKP)|
Rest of Quebec
*Source: Clin Genet: 2005:68:287-301
Symptoms of diseases
Tyrosinemia (type I) is an inherited metabolic disease characterized by a deficit of the enzyme necessary to degrade tyrosine, an amino acid present in the proteins of our diet. Inadequate degradation of tyrosine leads to an accumulation of toxic metabolic waste and damages the liver and kidneys.
Congenital lactic acidosis
Congenital lactic acidosis (also known as COX deficiency or French-Canadian Leigh syndrome) is also an inherited metabolic disease caused by the deficiency of an enzyme required for energy production in the liver and brain. Children who have the disease die on average before the age of six, usually as a result of acute lactic acidosis. No treatment exists for the moment.
Hereditary sensitivomotor neuropathy
Hereditary sensitivomotor neuropathy (with or without agenesis of the corpus callosum), also called Andermann or Charlevoix syndrome, is a hereditary neurological disease whose symptoms appear during the first year of life: absence of muscle tone and delayed motor development accompanied also a delay in intellectual development (mild to moderate). Progressive deterioration of the peripheral nerves leads to a loss of walking ability and progressive scoliosis in adolescence. Affected individuals have a life expectancy lower than that of the general population. This disease is incurable, but medications and treatments can relieve many symptoms.
Spastic recessive ataxia of Charlevoix-Saguenay (ARSACS)
Spastic recessive ataxia of Charlevoix-Saguenay (or ARSACS) is a hereditary neuromuscular disease. The affected child starts walking later than normal and stumbles more frequently; the disease is usually diagnosed around the age of 10. Intellectual abilities remain normal. Medications and treatments can relieve some symptoms.
Cystic fibrosis of the pancreas (CF)
It should be noted that cystic fibrosis is common not only in the Charlevoix and Saguenay Lac-Saint-Jean regions, but throughout Quebec. The carrier frequency is approximately 1 in 15 people in Charlevoix and the SLSJ and 1 in 25 elsewhere in Quebec.
Cystic fibrosis of the pancreas is the most common fatal genetic inheritance disorder in young Canadians, affecting primarily the lungs and digestive system. More than 3,000 people have the disease in Canada, and about 1 in 25 Canadians have a defective version of the gene responsible for FKP. Ever...