Monday, 24 January 2005
Last Updated Monday, 24 January 2005
What
Isovaleric Acidemia (IVA) is a rare, inherited condition caused by a missing or poorly functioning
enzyme named isovaleryl-CoA dehydrogenase. This
enzyme is important for the breakdown of protein in the body. During prolonged periods of fasting, protein from food and protein in the body’s muscles is broken down into
amino acids, which are then changed into glucose. Isovaleric acid is made during the breakdown of an amino acid named leucine. In IVA, isovaleric acid accumulates in the brain because it cannot be changed into glucose. As a result the brain is damaged and this leads to learning problems, loss of motor skills and seizures.
Who
IVA is estimated to occur in one out of every 50,000 children. Girls and boys of all races and ethnicities are affected equally.
Signs and Symptoms
Symptoms include poor feeding, vomiting, clumsiness, lethargy, seizures and coma. Symptoms are triggered by infections or by eating too much food with a lot of protein. A foul odor described as resembling sweaty feet, dirty socks, or cheese is commonly present. Children with IVA may become very sick during the first two weeks of life or have mild and repeated episodes of these symptoms throughout life.
Possible Causes
IVA is inherited in an
autosomal recessive manner and the
gene that makes this
enzyme is located on
chromosome number 15. In order to have this disorder both genes that make the IVA
enzyme must have a change (
mutation). The parents of an affected child are usually healthy, but each carries one copy of the mutated
gene. Carriers are healthy because they have one normal copy of the IVA
gene and this
gene makes enough
enzyme for the normal metabolism of protein. When both parents are carriers, there is a 25% chance of each of their children developing this disease. There is a 50% chance that each child will be a
carrier. IVA deficiency is not contagious or preventable.
Diagnosis
Blood and urine tests that are done when signs and symptoms are present will help make the diagnosis.
DNA testing is also available. Expanded newborn screening, as offered in some states, can detect IVA in the first few days of life.
Treatment
Treatment is aimed at limiting the intake of the amino acid leucine in the diet because it cannot be broken down when this
enzyme is not functioning properly. Children with this disorder are fed special leucine-free formulas. This special diet must be followed for life. Oral carnitine and glycine supplements can help the child’s body grow and develop. Carnitine and glycine bind to isovaleric acid to form nontoxic products, which can then be excreted in the urine. Aspirin interferes with this and therefore, children with IVA should not take aspirin.
Infections and fevers should be treated aggressively to prevent muscle breakdown. When the child is ill, dietary protein should be greatly reduced and replaced with carbohydrates. Also, carnitine doses may need to be increased.
Prognosis
Children with IVA can do well with early diagnosis and proper treatment. They can lead nearly normal lives as long as they follow the strict dietary requirements, consume the essential supplements, and take extra caution to avoid illness.
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
United Mitochondrial Disease Foundation
http://www.umdf.org
Non-profit organization providing support groups, education, information about research studies, counseling, and family networking.
Organic Acidemia Association
http://www.oaanews.org
Voluntary support group which represents children and adults with these disorders, their families and caregivers.
CLIMB (Children Living with Inherited Metabolic Diseases)
http://www.CLIMB.org.uk
National organization providing information, news, financial support and networking.
NIH/National Institute of Diabetes, Digestive and Kidney Diseases
Endocrine Diseases Metabolic Diseases Branch
www.niddk.nih.gov
National organization providing information, support, and newsletter.
Fatty Oxidation Disorders (FOD) Family Support Group
http://www.fodsupport.org
International coalition providing resources, education and networking.
March of Dimes Birth Defects Foundation
http://www.marchofdimes.com
Non-profit organization providing support groups, education, information about research studies, counseling, and family networking.
The Arc (a national organization on mental retardation)
http://thearc.org/
A national organization providing education, support and advocacy.
Google Search for Isovaleric Acidemia
References and Sources
www.savebabies.org/diseasedescriptions/iva.php
www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=243500
www.mchneighborhood.ichp.edu/pacnorgg/media/Metabolic/isovaleric_eng.pdf
www.my.webmd.com/hw/health_guide_atoz/nord504.asp
www.savebabies.org/familystories/justiceIVA.php
