Very few people will have heard of it: Canavan’s disease. Canavan’s disease is a recessively inherited condition in which the white matter of the brain is destroyed, which in short results in a general decline in development and body functions. It is a serious condition that greatly reduces life expectancy. Fortunately, the disease is not common: 1 in 6,400 children is born with it. What is striking is that the majority of these children are of Jewish descent and live in eastern Poland, Lithuania and western Russia. Yet Canavan’s disease occurs all over the world, including in the Netherlands. A YouTube video from 2012 shows twenty-six-year-old Kevin suffering from this disease. At the time, he was the second oldest alive in the world with this disease.
What is Canavan’s disease?
Canavan’s disease is a rare metabolic disease in which the white matter of the brain is destroyed. The body of children with this disease produces too much of a certain substance. This substance with the difficult name: N-acetylaspartylic acid, causes the white matter of the brain to be affected. The white matter is a fatty substance that ensures that information from the nerve cells is passed on to the muscles and the spinal cord. In Canavan’s disease, this white matter gradually turns into spongy material. It is obvious that the consequences of this are major.
What are these consequences?
The first symptoms of Canavan disease often manifest themselves about three to six months after birth. The baby is developing too slowly, feels weak, does not want to drink. Most children with Canavan never sit, walk or talk. Because the white matter does not function properly, important information necessary for intellectual development is not passed on. Many of these children remain ‘stuck in the baby phase’ and cannot do much more than lie down. At a later stage they become spastic and sometimes even completely paralyzed. They may also become blind or deaf, although the latter is less common. Many children with Canavan suffer from epileptic seizures. Life expectancy is short: the majority do not live longer than four years. Canavan disease is a serious condition that causes complete atrophy of the brain. There is no treatment for it, at most one can alleviate the symptoms and ensure that the child is lovingly cared for and can lie comfortably.
Autosomal recessive inheritance
Canavan’s disease is a hereditary disease. A congenital condition that you get through your parents. For many parents, this comes as a complete surprise, as they do not know that they themselves are carriers of this disease. You only get Canavan through recessive inheritance. If one of the parents passes on the dominant gene and the other passes on the recessive gene, there is nothing to worry about. The child is then only a carrier of the disease. When both parents are carriers and both pass on their recessive gene, the child will receive two recessive genes and therefore the disease. With this combination of parents he therefore has a 25% chance of inheriting the disease. Autosomal recessive inheritance therefore means that ‘the good gene predominates’. So you only get the disease if you inherit both the bad genes, from both your father and your mother. Fortunately, this is one of the reasons why the disease is rare. Of course, it is impossible for someone with Canavan disease to ever have children.
Hydrocephalus
As is the case with many metabolic diseases, the severity and progression of Canavan’s disease are determined by the extent to which the wrong substances that cause the problem are present in the body. When there is a lot of N-acetylaspartylic acid. is produced, the white matter will degenerate rapidly and the consequences will be noticeable quite soon after birth. The child will then not be older than four years old.
It may also be that the child appears to develop normally for a while and still has time to learn certain skills, such as sitting or grabbing something. As the disease progresses, the child loses these skills. There is also mental decline, making it increasingly difficult to contact the child. Because these children’s problems started a little later, they may also grow a little older. Ten years and in exceptional cases even twenty. Kevin, twenty-six, who can be seen in a video on You Tube (2012) was the second oldest in the world with this condition. His mother said he liked to be touched. She noticed this by the way he responded. This was almost imperceptible to the outside world, as Kevin could no longer do anything himself, he could not even move his arms and legs and functioned at the level of a baby.
The first thing you notice in babies with Canavan disease is that they develop a very large head. Parents often consult a doctor at this stage because they assume that their child has hydrocephalus. The head becomes enormously large in relation to the rest of the body, which often remains small and skinny. (thin arms and legs).
How is Canavan disease diagnosed?
In Canavan’s disease it is often initially thought that the child has hydrocephalus. The doctor will therefore first want to make an MRI scan of the head. This will quickly reveal that the child does not have hydrocephalus, but that the white matter of the brain is swollen and looks abnormal. This swelling causes the large head. If Canavan’s disease is suspected, the urine can be examined. In this study it is too much N-acetylaspartylic acid. easy to detect, as it is excreted in the urine.
No treatment
Canavan’s disease is a serious disease that is always fatal as there is no treatment. Since the white matter is essential for the functioning of the brain, all brain functions will eventually be lost and that is incompatible with life. All that remains is to treat the symptoms. You can think of medication against epilepsy or physiotherapy to keep the limbs somewhat flexible. Parents who are confronted with this disease have a difficult time to cope with their child who becomes increasingly needy, without any prospect of any improvement. Their hope is that the experimental gene therapy started in America will bear fruit. Through this therapy it is hoped to slow down or even stop the decline in children. Unfortunately, this is all still in its infancy and we are still waiting for an effective means to actually turn the tide for these children.
