Canavan disease is a myelin deficiency that results from a chromosomal mutation. Those affected show neurological deficits and usually die in their teens. So far, the disease is incurable despite gene therapy approaches.
What is Canavan disease?
A genetic leukodystrophy is known under the term Canavan disease. In 1931, Myrtelle Canavan first described the phenomenon. The autosomal recessive disorder is more common among Arab and Ashkenazi Jews than in the rest of the world. Like all lucodystrophies, Canavan’s disease is characterized by a lack of white matter in the brain. See lawfaqs for Definitions of Hyperkeratosis.
According to this, leukodystrophies are metabolic diseases that affect the myelin, which is relevant to the nervous system. Those affected suffer from progressive demyelination. Nerve pathways are impaired by the breakdown of myelin. Neurological deficits appear. Canavan disease is often referred to as spongy degeneration of the nervous system as the brain swells and the myelin becomes spongy.
Genetic storage diseases such as Krabbe’s disease must be distinguished from leukodystrophies such as Canavan ‘s disease. Krabbe’s disease also demyelinates the nervous system and both are caused by a chromosomal mutation. However, the affected chromosomes are different.
Causes
Biological transcription creates an image of strands of DNA, also known as mRNA. During biological translation, this mRNA is translated into protein sequences. In Canavan disease, a mutation occurs during these processes. These are mutations of the ASPA gene. This gene is located on the short arm of chromosome 17 and codes for the enzyme aspartoacylase. Aspartoacylase is found exclusively in the brain, where it breaks down N-acetylaspartate.
A mutation in the coding gene results in a deficiency of the enzyme. As a result, less N-acetylaspartate is broken down in the brain. The substance is therefore stored. This storage manifests itself in spongy changes and causes the brain to swell. The myelin in the brain is damaged and partially lost. Myelin nourishes, protects, and insulates nerve tissue. Damaged myelin conducts nerve impulses only slowly or not at all. In Canavan’s disease, the transmission of information between brain regions no longer works because of the processes described. Myelin loss is accompanied by secondary neuronal impairment.
Symptoms, Ailments & Signs
Children with Canavan’s disease are mostly normal immediately after birth. From the third month of life, the first symptoms appear in infantile forms of the hereditary disease. As a rule, the first symptoms concern psychomotor development. Head control is impaired and an oversized skull often develops. Those affected usually have a lack of tension in the muscles.
The further course of the disease is characterized by motor disorders such as the impossibility of walking, sitting and standing freely. Difficulty swallowing or seizures are also part of the clinical picture. Spastic paralysis often occurs. Perceptual centers of the brain can also be affected by demyelination.
As a rule, impairments in the ability to perceive primarily affect the eyesight. Complete blindness does not necessarily have to occur. The infantile form of Canavan disease is the most common. A distinction must be made between the congenital and the juvenile form. In the juvenile form, the first symptoms only appear after the first years of life.
Diagnosis & course of disease
The doctor mainly diagnoses Caravan’s disease using magnetic resonance imaging of the brain. In this imaging, the disease shows a relatively typical picture. The subcortical substance of the cerebrum and cerebellum shows lesions. This damage spreads centripetally over time. The symmetrically appearing lesions particularly affect the globus pallidus and the thalamus, but not the putamen or the caudate nucleus. The detection of increased N-acetylaspartate in the urine confirms the diagnosis.
Molecular genetic tests to detect the gene mutation are also possible. However, these complex procedures are not absolutely necessary, since increased N-acetylaspartate in the urine is specific to Canavan’s disease. The prognosis for the congenital form is unfavorable. Life expectancy is a few days or weeks. Patients with the infantile form usually reach their teens. In the juvenile form, the course of the disease is slower and patients are often older than 20.
Complications
Canavan’s disease leads to a greatly reduced life expectancy in most of those affected, so that the patients die at a young age as teenagers. The disease also has a strong effect on relatives and parents, so that they suffer from severe psychological problems or depression. Treatment by a psychologist is necessary in many cases, especially after death.
The patients mainly suffer from paralysis and severe limitations in sensitivity. Those affected may also be dependent on the help of their parents in their everyday life in order to be able to cope with it. Movement is restricted and the patient’s quality of life decreases significantly. Spasms and seizures also occur with this disease.
It is not uncommon for those affected to also suffer from visual or hearing problems. They also require special support and are significantly limited in their development. Canavan’s disease can be limited by various therapies, but a complete and, above all, causal treatment is not possible. There are no further complications during the treatment itself. However, the life expectancy of the patient is significantly reduced by the diseases.
When should you go to the doctor?
In Canavan’s disease, the first signs of an irregularity usually appear within the first six months of life, but they are rarely noticeable immediately after birth. If there are disturbances in the movement sequences and general motor skills in the growth and development process of the child, a doctor’s visit is advisable. If weak muscles appear when gripping, this is a cause for concern and should be examined by a doctor. If there are significant delays in development compared to children of the same age, a doctor should be consulted. Targeted tests can be used to determine an objective assessment of the state of health and treatment can be initiated.
If the child does not learn to walk, sit or stand independently, this is considered unusual. A doctor is needed to investigate the cause. Cramps, seizure disorders and spasticity should be examined and treated by a doctor. If paralysis occurs on the body, a doctor should be consulted immediately.
The child needs medical care to ensure relief from the symptoms. Delayed perception and processing of sensory stimuli should be clarified by a doctor. Decreased vision or hearing are characteristic of the condition and require treatment. In severe cases, the patient becomes blind. Therefore, a doctor should be consulted as soon as possible at the first irregularities or the suspicion of a malfunction.
Treatment & Therapy
Canavan’s disease is incurable. So far, instead of causal therapies, there are only supportive therapy options. Even the delay of the disease and a secured prolongation of life are not feasible so far. The supportive therapeutic approach depends on the symptoms. Restlessness, pain and seizures can be alleviated with drug therapies, for example. In the case of functional disorders of the respiratory system, a breathing aid should be considered.
The relatives of those affected often also receive additional therapeutic care. As a rule, a psychotherapist is assigned to them. Gene therapy approaches to cure the disease have been in the works for several years. As part of the gene therapy treatment, the ASPA gene is to be introduced into the patient’s brain via a viral gene shuttle made of adenoviruses.
In the animal model, the concentration of N-acetylaspartate in the urine was reduced by this measure. Despite these partial successes, the myelin remained spongy. Nevertheless, medical research is currently still trying to develop a causal therapy. An improvement in the gene shuttles has already taken place, but has still not been able to deliver any groundbreaking successes.
Outlook & Forecast
The prognosis of Canavan’s disease depends on the form of the disease. The infantile form is fatal. Most children die in their second year of life. Other forms offer a life expectancy of five to ten years. The exact determination of the mutation is decisive for the prognosis.
Canavan’s disease takes a progressive course. Associated with this, the physical and mental abilities decrease and the quality of life of the child decreases continuously. The relatives are also heavily burdened by the suffering. They usually require therapeutic advice and comprehensive care. There is no prospect of a cure for Canavan’s disease. However, the symptoms can be alleviated by symptomatic therapy. Gene therapy has also been available for several years, through which the gene is supposed to be introduced into the brain. So far, this treatment has not been approved for humans.
With an early diagnosis, the sick children can live a short but relatively symptom-free life. In the mild form of the disease, life expectancy is normal. Various therapeutic approaches have been developed in recent years and significantly improve the prognosis. As a result, the prognosis is favorable for mild Canavan disease, but significantly worse for the severe form.
Prevention
Genetic diseases such as Canavan’s disease cannot be prevented. However, couples planning a family can have their risk assessed using molecular genetic tests.
Aftercare
In most cases, those affected with Canavan’s disease have only very few or limited follow-up measures available. For this reason, the person affected by this disease must ideally consult a doctor very early on in order to prevent the further occurrence of complications and symptoms. Since it is a genetic disease, it cannot usually be completely cured.
Therefore, if the person concerned wants to have children, they should have a genetic examination and counseling carried out in order to prevent the disease from recurring in their descendants. Most patients are dependent on taking various medications to relieve the symptoms. It is always important to ensure that it is taken regularly and that the dosage is correct.
If anything is unclear or if you have any questions, you should first consult a doctor. Furthermore, most of those affected are dependent on the help and support of their own families in their everyday lives. Loving conversations also have a positive effect on the further course of the disease and can prevent depression and other mental upsets.
You can do that yourself
Canavan’s disease is almost always fatal. The most important self-help measure for many parents is to get in touch with other relatives. Suitable contact points are self-help groups and forums on the Internet. In order to enlighten the child about his illness, a specialist center for nervous diseases should be visited. In the course of this, parents can find out about novel treatment options, for example gene therapy, which is intended to make Canavan’s disease curable in the future.
If the course is positive, the necessary nursing staff and conversions in your own home should be organized at an early stage so that the child can be treated easily. An adapted diet and moderate exercise can further improve the quality of life. Nevertheless, Canavan’s disease always takes a severe course. Family members should speak to their doctor about palliative care options.
In families where cases of Canavan disease have been observed, the necessary genetic testing should be carried out. An ultrasound examination can be used to determine whether the child has Canavan’s disease. After the diagnosis, the necessary measures can be taken to enable the patient to lead a relatively symptom-free life.
