All about Canavan

What is Canavan Disease?

Canavan disease is a rare inherited disease that affects the white material of the brain. It harms the capability of nerve cells (neurons) in the brain to send and receive messages. It comes under the group of genetic disorders known as leukodystrophies that affect the growth or maintenance of the myelin sheath, which is the covering that guards nerves and promotes the competent transmission of nerve impulses. The symptoms in the affected infants usually do not appear for the first few months but by the age of 3 to 5, the signs and symptoms start appearing and affect the brain, spinal cord, and nerves, and symptoms worsen over time.

What are the Types of Canavan Disease?

Canavan disease mostly starts appearing during infancy or early childhood. It can be categorized into two types:

• Infantile Canavan Disease: It is the most common type of Canavan disease and is more severe. Infants with Canavan disease do not live more and often die in childhood or adolescence.
• Juvenile Canavan Disease: It is less common and milder as compared to infantile Canavan disease. It is not life-threatening and doesn’t shorten a person’s life.

What are the Symptoms of Canavan Disease?

The symptoms of Canavan disease may vary according to its severity

Some common symptoms of Canavan disease are:

• Abnormally large head
• Poor coordination to control head and neck
• Decreased visual responsiveness and tracking
• Strange muscle tone, resulting in stiffness or limpness
• Unusual body posture
• Trouble eating food, especially swallowing
• Problems in sleeping
• Seizures
• Intellectual disability
• Quiet or impassive behavior, showing very less interest or emotion.
• Muscle spasms

What are the Causes of Canavan Disease?

Canavan disease is one of the numerous genetic disorders known as leukodystrophies and since it’s an inherited disease, it can be transmitted from parents to children.

The main reason for this disease is the disruptions or changes (mutations) to the aspartoacylase (ASPA) gene. This mutation is inherent as an autosomal receding characteristic.

For a child to develop Canavan disease both of his/her parents must carry the defective gene that causes an absence of ASPA. When both parents have the gene, each child will have a 25 percent chance of getting this genetic disorder

People diagnosed with Canavan disease don’t have sufficient ASPA, and because of it, NAA starts to develop in brain tissue. This harms their myelin (white matter), a fatty element that protects and nurtures nerves in the brain and spine. Over a period of time, it causes their brain to depreciate into spongy tissue with lots of tiny fluid-filled spaces. It also averts their brain from sending and receiving nerve signals appropriately.

What are the Risk Factors of Canavan Disease? 

• Hereditary: Canavan disease is an inherited disease and the main risk factor of this disease is when both parents are carriers of the defective gene and it can pass down to their children. If both parents carry the Canavan gene mutation, there is a one in four (25 percent) chance with each pregnancy that the child may be born with Canavan disease.
• Ethnicity: Even though the Canavan disease may happen to people from any ethnic group, but it is more found that Ashkenazi Jews from eastern Poland, Lithuania, and western Russia, and Saudi Arabians are more prone to it. Roughly one in 55 Ashkenazi Jews has the Canavan disease genetic mutation. Though researchers still don’t know the exact reason behind it but genetics may be one of the reasons why people from this particular ethnic group have more risk of developing Canavan disease.

What are the Complications of Canavan Disease?

Canavan disease is a life-long condition and in some cases, it is life-threatening also. Subject to the severity of the condition, children who are suffering from Canavan disease generally can’t sit up, crawl, or walk. They may also find it difficult in swallowing food and also experience delayed overall development physically and mentally. Language and other skills develop late, if at all as compared to other children. These complications can have a direct impact on a child’s quality of life. With time the condition may worsen and problems like paralysis, blindness, or hearing loss may also occur.

How Canavan Disease is Diagnosed?

A diagnosis of Canavan disease may be carried out among the infants with noticeable disorders such as poor head control, macrocephaly, etc. A diagnosis may be established by a comprehensive clinical assessment, a detailed patient history, and a variety of specialized tests including:

• Blood or Urine Test: Blood or urine tests are done for the levels of NAA or ASPA or tests that are done for the genetic mutation. Lab tests of specific skin cells (called cultured fibroblasts) are done to check the lack of ASPA.
• Amniocentesis: Among infants, Canavan disease may be diagnosed before the child is born through amniocentesis. Amniocentesis is a test where a sample of the fluid that surrounds your fetus to taken to check the levels of NAA. It’s generally performed on 15 to 20 weeks pregnant women.
• Chorionic Villus Sampling (CVS):  Chorionic villus sampling (CVS) is a test available for parents who are at high risk of Canavan disease or carry a known genetic mutation. Here a tissue sample from your placenta is taken to test for the genetic mutation. It’s generally performed on 10 to 12 weeks, pregnant women.

What are the Treatment Options Available for Coronary Artery Disease (CAD)?

 There is no cure, nor is there a standard course of treatment available for this disease yet and the treatment is symptomatic and supportive to ease down the symptoms such as:

• Feeding tubes to provide nutrition and fluids.
• Medicines are available to control seizures (anticonvulsants).
• Physical therapy to better posture and communication skills.

Living with Canavan Disease

Canavan disease is a life-long condition and children with infantile Canavan disease usually do not survive more than 10 years and in some cases, a few may survive into their teens or 20s. But in mild juvenile Canavan disease, life expectancy is generally normal. Living with Canavan disease is not easy as people with this disease have lower mental and physical capabilities than normal people. To live a considerably dignified life, people with Canavan disease can go for counseling (talk therapy) and get involved with organizations that support patients and research.

Whom to Consult?

If you have a family history of Canavan disease then there is a high chance of your child developing Canavan disease. If you are expecting a child then discuss with your doctor about the care your child will need and whether your family members can have DNA tests to see if they carry the genetic mutation. Both parents need to have a Canavan gene mutation for their baby to develop the disease. Testing can help them make informed decisions about having children and prepare themselves accordingly.