Canavan disease is a rare inherited disorder that impacts the ability of nerve cells in the brain to receive and transmit messages. Canavan disease is one of many genetic diseases called leukodystrophies which disrupt maintenance or growth of the myelin sheath, or the protective covering of nerves.
Canavan disease is caused by mutations in the ASPA gene, which gives instructions for producing the enzyme aspartoacylase. This enzyme is responsible for breaking down a compound called NAA found in neurons. While the function of NAA is not fully understood, it is believed to play an important role in producing myelin sheath or transporting water out of neurons.
The most common and severe form of the disease is neonatal. Infants with Canavan disease usually begin displaying symptoms around the age of 3 to 5 months, when developmental problems become apparent. Infants with the disorder do not develop important motor skills like the ability to sit without support or control head movement.
The disease is also characterized by hypotonia (weak muscle tone), macrocephaly (large head size), and irritability. Infants may also display sleep disturbances, seizures, and trouble swallowing.
There is also a juvenile form of Canavan disease that is less common. This form causes mild delays in motor skills and speech in childhood.
Most people with neonatal Canavan disease do not live past childhood, but some survive into adolescence. Individuals with the mild form do not seem to have a shortened lifespan and the disorder may be so mild that it is never recognized as Canavan disease.
Canavan disease is a progressive and fatal form of brain atrophy. There is no cure or standard treatment for the disorder.
Canavan disease is inherited in an autosomal recessive pattern. This means both inherited genes must have mutations. A parent with only one copy of the mutated gene is a carrier and typically displays no symptoms of the disorder. A child has a 25% chance of having Canavan disease if both parents are carriers, a 50% chance of being a carrier for Canavan, and a 25% chance of inheriting two non-mutated copies of the gene.
The disease is most often found in people of Ashkenazi Jewish ancestry. About 1 in 40 Ashkenazi Jews are carriers of the Canavan gene. If you are worried you are a carrier for Canavan disease or you have a family history of the disorder, carrier DNA testing for Canavan disease is available through a simple blood test to check for a defective copy of the ASPA gene.