Five recessive diseases are particularly common in the Charlevoix and Saguenay Lac-Saint-Jean (SLSJ) regions:

  • Tyrosinaemia
  • Congenital Lactic Acidosis
  • Hereditary Motor and Sensory Neuropathy
  • Recessive Spastic Ataxia of Charlevoix Saguenay
  • Cystic Fibrosis

Heredity factors for recessive disease

A recessive disease occurs when a person inherits two copies of a defective gene.

A person whose cells have only one abnormal gene is called a carrier but it not affected with the disease. Each time two parents who are carriers have a child, there are three possible scenarios: 25% chance that the child will be unaffected and non-carrier, 50% chance that the child will be unaffected but will be a carrier and a 25% chance that the child will be born with the disease.

The frequency of being a carrier

The carrier frequency is similar for each of these diseases, about one individual in 20. The detection rate is 93% to 99% in French Canadians. At this time, only those individuals who already have a known case in their family or their partner is known to be a carrier can turn to the Canadian Public Health system for screening. However, it is possible to get genetic screening tests performed at Procrea Fertility to find out your carrier status.

Component: Data Table Block


DiseaseIncidence*
of Children Affected at Birth Charlevoix SLSJ
Carrier Frequency*
in the Charlevoix SLSJ Population
Tyrosinaemia1/1,8001/21
Congenital Lactic Acidosis1/2,0001/23
Hereditary Motor and Sensory Neuropathy with or without Agenesis of the Corpus Callosum (ACCPN)1/2,1001/23
Autosomal Recessive Spastic Ataxia of Charlevoix Saguenay
(ARSARCS)
1/1,9301/22
Cystic Fibrosis (CF)
Charlevoix SLSJ
1/1,000
1/15
Cystic Fibrosis (CF)
Rest of Quebec
1/2,5001/25
*Source: Clin Genet: 2005:68:287-301
Disease Incidence*
of Children Affected at Birth Charlevoix SLSJ
Carrier Frequency*
in the Charlevoix SLSJ Population
Tyrosinaemia1/1,8001/21
Congenital Lactic Acidosis1/2,0001/23
Hereditary Motor and Sensory Neuropathy with or without Agenesis of the Corpus Callosum (ACCPN)1/2,1001/23
Autosomal Recessive Spastic Ataxia of Charlevoix Saguenay
(ARSARCS)
1/1,9301/22
Cystic Fibrosis (CF)
Charlevoix SLSJ
1/1,000
1/15
Cystic Fibrosis (CF)
Rest of Quebec
1/2,5001/25
*Source: Clin Genet: 2005:68:287-301

Disease Manifestation

Tyrosinaemia

Tyrosinaemia (type I) is a hereditary metabolic disorder characterized by an enzyme deficiency. Failure to properly break down tyrosine leads to the accumulation of toxic metabolic waste and brings liver and kidney damage.

Congenital Lactic Acidosis

Congenital lactic acidosis (also known as COX deficiency or French Canadian type Leigh syndrome) is also a hereditary metabolic disorder caused by the lack of an enzyme necessary to produce energy in the liver and the brain. On average, affected children die before the age of 6, generally following an acute lactic acidosis episode. At this time, there is no treatment for the disease.

Hereditary Motor and Sensory Neuropathy (ACCPN)

Hereditary motor and sensory neuropathy (with or without agenesis of the corpus callosum), also known as Andermann or Charlevoix syndrome, is a hereditary neurological disease with symptoms surfacing in the first year of life: lack of muscle tone and, slow motor development accompanied by delayed mental development (light to moderate) and progressive peripheral nerve deterioration.

Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS)

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (or ARSACS) is a hereditary neuromuscular disease. The affected child begins to walk later than normal, stumbles more often and the disease is usually diagnosed at 10 years of age. Mental abilities remain normal. Medication and treatment can relieve some of the symptoms.

Cystic Fibrosis (CF)

It should be noted that Cystic Fibrosis is common not only in the Charlevoix and Saguenay Lac-Saint-Jean regions, but everywhere else in Quebec. The carrier frequency is about 1 in 15 people in the Charlevoix and SLSJ regions and 1 in 25 everywhere else in Quebec.


Cystic Fibrosis

Cystic Fibrosis is a hereditary genetic disorder primarily affecting the lungs and the digestive system. It is caused by a malfunction of the mucus producing glands. Cystic Fibrosis is the most common fatal inherited disease affecting young Canadians. More than 3,000 people in Canada have CF and about 1 in 25 Canadians is a carrier of a defective version of the gene responsible for Cystic Fibrosis. Every year, one in every 3,300* children born in Canada is diagnosed with the disease.

Symptoms

Cystic Fibrosis causes a build-up of thick mucus in the lungs leading to severe respiratory problems. Moreover, mucus and protein build-up in the digestive tract results in extreme difficulty in digesting and absorbing adequate nutrients from food. The effects of CF are most devastating in the lungs.

Fertility & Cystic Fibrosis

As Cystic Fibrosis can affect mucus viscosity, fertility may also be compromised. In women with the disease, the fluidity of vaginal secretions varies because the mucus is often thicker. This makes it more difficult for the sperm to travel and for fertilization to occur. Therefore, it often takes longer for women with Cystic Fibrosis to become pregnant. Regrettably for men, in most cases, Cystic Fibrosis leads to infertility (not to sterility). Sperm cell production is normal, the problem occurs in the testicle, where a blockage or absence of the vas deferens may make the passage of sperm impossible.

A Test to Gain Knowledge

A genetic screening test can determine your carrier status. At this time, only those individuals who already have a known case in their family or their partner is known to be a carrier can turn to the Canadian Public Health system for screening. However, it is possible to get this genetic screening test performed at Procrea Fertility to find out your carrier status.

*SOGC, 2002, no. 118 – Cystic Fibrosis Carrier Testing in Pregnancy in Canada