Canavan Disease
Description
Canavan disease is a rare, inherited metabolic disorder that primarily affects the brain. It is caused by a deficiency in the enzyme aspartoacylase, leading to the accumulation of a harmful substance called N-acetylaspartate (NAA) in the brain. This accumulation disrupts brain development and function, resulting in a range of neurological symptoms.
Genes Involved
Canavan disease is caused by mutations in the ASPA gene, located on chromosome 17. This gene provides instructions for making the enzyme aspartoacylase, which is essential for breaking down NAA.
Recognizing the Signs and Symptoms
Symptoms of Canavan disease typically appear in infancy, often within the first few months of life. These may include:
- Delayed development: Slow milestones such as rolling over, sitting up, or crawling.
- Muscle weakness and hypotonia: Floppy limbs and decreased muscle tone.
- Seizures: Uncontrolled electrical activity in the brain, causing shaking or other unusual movements.
- Vision problems: Nystagmus (rapid eye movements) and strabismus (misaligned eyes).
- Head growth abnormalities: Macrocephaly (abnormally large head) or microcephaly (abnormally small head).
- Progressive neurological decline: Worsening symptoms over time, including intellectual disability, loss of motor function, and behavioral problems.
Causes
Canavan disease is an autosomal recessive disorder, meaning that both parents must carry the mutated ASPA gene to pass it on to their child. If both parents are carriers, there is a 25% chance of their child inheriting the disorder.
Inheritance/recurrence risk
The inheritance pattern of Canavan disease is autosomal recessive. This means that both parents must carry the mutated gene for a child to inherit the disease. If both parents are carriers, there is a 25% chance that each child will inherit the disease, a 50% chance that each child will be a carrier, and a 25% chance that each child will not inherit the gene at all.
Recurrence risk for future pregnancies is determined by the carrier status of the parents.
