Canavan disease is a rare genetic disease that results in progressive damage to brain cells. It is most common among Ashkenazi Jews.
Genetics Home Reference noted that the incidence of Canavan disease among Ashkenazi Jews is one in 6,400 to 13,500 individuals. It is unknown what the incidence of the disorder in other populations are.
The condition is caused by mutations of the ASPA gene. Normally, the ASPA gene is involved in the production of aspartoacylase, an enzyme that breaks down N-acetyl-L-aspartic acid, or NAA.
The purpose is NAA is not fully known, but Genetics Home Reference stated that it might be involved in the production of myelin, which covers nerve cells.
For an individual to have Canavan disease, she must receive an affected gene from each parent.
The mutations in Canavan disease affect the normal breakdown of NAA, which results in damage to the myelin. Without proper myelin sheath around the nerve cells, the cells cannot communicate properly.
The brain degenerates, with the brain looking like spongy tissue with microscopic fluid-filled spaces, according to the National Institute of Neurological Disorders and Stroke.
The symptoms of Canavan disease first appear around ages 3 to 6 months. MedlinePlus noted that the disease may first be noticed when the child does not meet certain developmental milestones.
The child may have issues controlling her head, increasing head size, abnormal posture with straight legs and flexed arms, and poor muscle control, especially poor control of the neck muscles. Nasal regurgitation may occur, in which there is a backflow of food that goes into the nose.
Reflux with vomiting, swallowing difficulties and feeding problems may occur. Other symptoms of Canavan disease include irritability, blindness, seizures, poor visual tracking, and severe intellectual and development disability.
Prognosis for Canavan disease is poor. The National Institute of Neurological Disorders and Stroke noted that usually, individuals with the disease die before age 10. However, some individuals survive into their twenties.
In terms of treatment, there is no standard course, and it tends to target the symptoms of Canavan disease, according to the National Institute of Neurological Disorders and Stroke.
But a new preliminary study may have found a possible treatment for Canavan disease. The researchers used a gene therapy method that was developed at the University of North Carolina School of Medicine.
It involves taking a normal copy of the ASPA gene and putting it into a non-infectious virus. It is then directly infused in patients’ brains. This gene therapy reduces the levels of NAA and slowed neuronal degeneration.
The study by Leone et al. treated a total of 13 children, all of whom are still alive about a decade later.
The gene therapy resulted in small improvements in symptoms, such as muscle rigidity and ability to move. It also reduced the number of seizures in some of the children.
In the beginning of the study, the gene therapy was administered to children who were 5 years old on average. HealthDay News noted that this group showed the least amount of improvement.
As the study progressed, gene therapy was allowed on younger participants — 16 months old on average — who displayed the most benefit from the treatment.
While this treatment is showing promise for patients with Canavan disease, it is still experimental and not approved as a treatment in the United States. In addition, there is not good natural history data on this disease.
References
Genetics Home Reference. Canavan Disease. Web. 24 December 2012.
http://ghr.nlm.nih.gov/condition/canavan-disease
National Institute of Neurological Disorders and Stroke. Canavan Disease Information Page. Web. 24 December 2012.
http://www.ninds.nih.gov/disorders/canavan/canavan.htm
MedlinePlus Medical Encyclopedia. Canavan Disease. Web. 24 December 2012.
http://www.nlm.nih.gov/medlineplus/ency/article/001586.htm
Leone, P. et al. (19 December 2012). “Long-Term Follow-Up After Gene Therapy for Canavan Disease.” Science Translational Medicine. Web. 24 December 2012.
http://stm.sciencemag.org/content/4/165/165ra163.abstract
HealthDay News. Gene Therapy Shows Promise for Rare Children’s Brain Disorder. Web. 24 December 2012.
http://consumer.healthday.com/Article.asp?AID=671815
Reviewed December 24, 2012
by Michele Blacksberg RN
Edited by Jody Smith