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Madisons Foundation - Moms And Dads In Search Of Needed Support
What
Canavan disease is a rare, inherited disease of the brain and nervous system which results in progressive loss of function. Developmental delays usually begin in early infancy and progress to severe disability in the early teen years requiring complete assistance with activities of daily living.
Who
Canavan disease is inherited in an autosomal recessive fashion, which means that the child with the disease inherits an affected gene from each parent. The exact frequency of the disease is not known; however, it is most often found in children of Eastern and Central European Jewish descent (Ashkenazi). Within the Ashkenazi Jewish population, it is estimated that 1 of every 40 people have a single copy of the affected gene which they can then pass on to their children. There is no known difference in frequency between males and females.
Signs and Symptoms
By 3 to 5 months of age, children with Canavan disease usually show the following:
- Large head size (macrocephaly) with poor head control;
• Developmental delays which become more pronounced over time, including the inability to sit, walk, or stand;
- Poor speech and language which may lead to the inability to speak;
- Poor muscle tone (hypotonia) which progresses to spasticity (stiffness of the arms and legs);
- Seizures;
- Feeding difficulties including reflux disease and sleep problems;
- Occasionally blindness;
• Abnormal breathing patterns with episodes of shallow or absent breathing (apnea); and irritability.
Although children with Canavan disease can have multiple problems with blindness and development, they do usually have normal hearing.
Possible Causes
Canavan disease belongs to a group of disorders known as the leukodystrophies, which are a group of inherited neurological disorders that affect the growth and function of myelin, a protein that insulates nerves in the brain. The absence of a key enzyme called aspartacylase (ASPA) leads to the build-up of harmful substances in the brain which destroy myelin. This results in the neurological changes seen in Canavan disease. The most common reason that the ASPA enzyme is unable to function is due to the genetic defect in the enzyme.
Diagnosis
The disease is diagnosed by checking the amount of active ASPA enzyme in skin cells or the amount of the harmful breakdown product of ASPA (known as NAA). When ASPA levels in the blood are low and NAA levels in the blood or spinal fluid are high, the diagnosis is fairly certain.
Prior to a child being born, the amniotic fluid can be checked for the specific gene changes and the results may be helpful in counseling the families for future pregnancies. Similar testing on blood can be done after the child is born. There are tests available which check for the 2 most common gene changes. These tests have been found to be very good for finding the altered genes in the Ashkenazi Jewish population. In populations other than the Ashkenazi Jewish, however, the tests are not as good at detecting the gene problems because the disease is much less common and there is a higher likelihood that other gene changes can cause Canavan disease in these groups.
Treatment
There is unfortunately no cure for Canavan disease. Treatment is focused on providing adequate nutrition, treating seizures, and controlling infections. Many children will require placement of a feeding tube to receive adequate nutrition. If the child develops seizures, medications can be started to help control them. There is currently research in progress that is focused on investigating the role of gene therapy in treating children with Canavan disease. They are looking to see if inserting genes that produce normally functioning ASPA enzyme into stem cells. Also, there is some research into whether certain medications will help decrease the amount of NAA, the harmful byproduct.
Prognosis
Children with Canavan disease have a very shortened lifespan with survival determined by how young the child is when he or she started having symptoms. Survival is typically only weeks if the baby has symptoms at birth. If the symptoms present a little later but still in the infancy period, survival may be into childhood, but most die in the first few years of life. Children who are older when the symptoms begin may survive to the teenage years.
Connect with other parents
In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.Weblinks
National Institute of Neurological Disorders and Stroke
http://www.ninds.nih.gov/health_and_medical/disorders/canavn_doc.htm
National organization for families affected by this disorder.
The National Tay-Sachs and Allied disorders website
http://www.ntsad.org/
Informative website for parents.
The Canavan Foundation
http://www.canavanfoundation.org/
National organization centered on building awareness and support. This website also has links to other diseases which occur in Ashkenazi Jewish patients and lists available testing centers in the U.S.
Canavan Research Foundation
http://www.canavan.org/
Learn about the latest research going on.
Canavan Research Illinois
http://www.canavanresearch.org/
More on the latest cutting-edge research with a good diagram that explains the role of myelin.
Jewish Genetic Diseases
http://www.mazornet.com/genetics/canavan.asp
Parent friendly resources for the appropriate ethnic background.
REFERENCES AND SOURCES:
NIH Genetics Home Reference
http://ghr.nlm.nih.gov/ghr/disease/canavandisease
Helpful resource for parents from a reliable source.
NORD. "Canavan Disease." National Organization of Rare Disorders, http://www.rarediseases.org/search/rdbdetail_abstract.html?disname=Canavan%20Disease. Accessed January 15, 2007.
OMIM. "Canavan Disease." Online Mendelian Inheritance in Man: Johns Hopkins University. http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=271900. Accessed January 15, 2007.
Roman, A. "Prenatal screening for genetic disease in the Ashkenazi Jewish population." UpToDate. Online http://www.uptodate.com/. Accessed January 15, 2007.