Canavan Disease

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Mutations in the ASPA gene cause Canavan Disease. This gene is used to make an enzyme which breaks down a compound called NAA in the brain. Without the ability to break it down, levels of NAA rise in those with Canavan Disease, creating a chemical imbalance leading to the symptoms described, although the role of NAA and how this causes these symptoms are not well understood. In the milder form of Canavan Disease, the enzyme’s activity is not so impaired, so NAA does not accumulate to such high levels.

Canavan Disease is most common in people with Ashkenazi Jewish ancestry.

This condition is rare, it effects approximately 1 in 50 people, in Ashkenazi Jewish populations, in other populations, this figure is unknown. It is believed to affect males and females equally.

The most common form of Canavan disease is the severe infantile form. Affected people are usually normal at birth. Development problems become noticeable at around 3-5months, as infants do not develop motor skills such as the ability to turn over, sit without support or control head movements. They may also have symptoms such as hypotonia (reduced muscle tone) and a large head (macrocephaly). Infants with Canavan disease may have difficulties in feeding and swallowing, poor vision, disturbed sleep, irritability and seizures. Most with the severe form of Canavan disease do not survive into adolescence.

Mild/juvenile Canavan disease causes mild developmental delay, including delay to speech and motor skills. These may be so mild that they are never identified as Canavan disease, and may not have an effect on life expectancy.

Diagnosis may be determined by the acknowledgement of physical symptoms and a patient and family history. Diagnosis can also be made through biochemical testing of blood samples and testing urine samples for high levels of NAA within them.

There is no cure for this disorder. Treatment is currently based on the individual symptoms which are present, avoiding complications, and providing support for your child and your family as a whole.

In the severe forms of Canavan disease treatment is supportive and directed to providing adequate nutrition and hydration, managing infectious diseases, and protecting the airway. Hospice care is a resource used by the families of the individuals affected by the disease.

The following therapies and treatments (amongst others which are deemed necessary) may be used to alleviate and manage symptoms:

• Physical therapy to minimize contractures and optimize abilities and seating posture

• Other therapies to enhance communication skills (especially in those with a more gradual clinical course), and

• Early intervention and special education programs.

• Seizures may be treated with antiepileptic drugs.

• A feeding gastrostomy may be required to maintain adequate intake and hydration in the presence of swallowing difficulties.

• Botox® injections may be used to relieve spasticity.

In the mild/juvenile form of Canavan disease, treatment may involve speech therapy or tutoring but often they require no special medical care.

Humans have chromosomes composed of DNA. Genes are pieces of DNA that carry the genetic instruction. Each chromosome may have several thousand genes.

The word mutation means a change or error in the genetic instruction.

We inherit particular chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instruction that determines characteristics, which are a combination of the parents.

This is an inherited condition. There is nothing that could have been done to prevent your baby from having this condition.

Everyone has a pair of genes that make the enzyme which breaks down NAA. In children with Canavan disease, neither of these genes works correctly. These children inherit one non-working gene from each parent.

Parents of children with Canavan disease are carriers of the condition. Carriers do not have the disorder because the other gene of this pair is working correctly.

When both parents are carriers, in each pregnancy the risk to the baby is as follows:

• There is a 25% chance (1 in 4) of the baby having Canavan disease.
• There is a 50% chance (1 in 2) for the baby to be a carrier of Canavan disease.
• There is a 25% chance (1 in 4) for the baby to have two working genes and neither have Canavan disease nor be a carrier

Thank you to Alex TLC for helping provide this up-to-date information.

Established in 2004, Alex TLC provides support for all those with a genetic leukodystrophy and are also an internationally recognised centre of excellence for those affected with adrenoleukodystrophy and adrenomyeloneuropathy.

Alex TLC Contact Details:

• Phone 020 7701 4388
• Email info@alextlc.org
• Website https://www.alextlc.org/

References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing contact@metabolicsupportuk.org [Resource Library No: CAP032].