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Short Chain Acyl CoA Dehydrogenase Deficiency (SCA
Monday, 18 August 2003
Wednesday, 04 February 2004
Acyl-CoA Dehydrogenase Deficiency, Short-Chain; Lipid-Storage Myopathy Associated with SCAD Deficien

What

Short Chain Acyl-CoA Dehydrogenase Deficiency (SCAD) is a condition in which the body cannot break down certain types of fats. When a person eats food with fat, the body stores it in the form of "fatty acids". Fatty acids come in different lengths: long, medium, and short. In SCAD, the affected person cannot break down the short length fatty acids. Thus, it is classified under a group of conditions known as "fatty acid oxidation disorders". Enzymes are responsible for performing the job of breaking down fatty acids. But in SCAD, the enzyme is either missing or does not perform its job correctly. This enzyme is called "short chain acyl-CoA dehydrogenase". Because this enzyme is missing, acids and ammonia can accumulate in the blood, which is why SCAD also belongs to a group of disorders known as "organic acidemias".

Who

SCAD deficiency is a rare genetic disorder. It can affect both boys and girls.

Signs and Symptoms

Symptoms of SCAD may start in infancy or in adulthood. When symptoms start in infancy, the signs occur throughout the body. Infants may have weak and abnormal muscles in which their bodies may be limp (hypotonia) or stiff (hypertonia). They may have poor eating and vomiting which results in poor growth and be described as failure to thrive. Infants may develop seizures, and they may have slow development or be delayed as compared to other children their age. They may breathe rapidly if acids are building up in their blood. Also, they may have low blood sugars (hypoglycemia). As they get older, these children may become hyperactive. When symptoms begin during adulthood, people are usually affected mostly in their muscles. Their bodies may be limp (hypotonia) or stiff (hypertonia), and they may have neurologic problems (or problems with their nerves).

Possible Causes

All of us have genetic material that makes us who we are. The genetic material, referred to as “chromosomes” are numbered. The gene for SCAD has been found on chromosome 12 called the ACADS gene. Mistakes in this gene cause SCAD. SCAD is an autosomal recessive disorder. This means that each parent has one abnormal gene on chromosome 12 and one normal gene on chromosome 12. Because each parent has one normal gene, they themselves do not have SCAD. However, when the child receives one abnormal gene from the mother and one abnormal gene from the father, the child has two affected genes on chromosome 12. In autosomal recessive diseases, when a child has two abnormal genes, he/she is affected with SCAD.

Diagnosis

When the diagnosis of SCAD is suspected because of the child's symptoms, a special blood test can be performed to confirm the diagnosis. If needed, a small piece of muscle can be taken (a muscle biopsy) and analyzed.

Treatment

Treatment of SCAD is mostly related to diet. It is important for those with SCAD to avoid what they cannot digest -- short-chain fatty acids. Foods like butter and oil have a high concentration of these fatty acids. Also, it is important to avoid long periods of time without eating by having frequent meals. When children with SCAD get sick with a virus, flu or cold and cannot eat, they may have to get their nutrition through their veins (or IV, intravenously). Also, a supplement called carnitine is used for some children because it helps to get rid of acids that may build up in the blood. Carnitine is a natural substance found in foods and is not harmful.

Prognosis

Fatty acid oxidation disorders, such as SCAD, have a large range of severities and prognoses. Severity of this disorder depends on how much of the enzyme (described above in the "What" section) is available in the child's body. If the child has an abnormal gene that causes him/her to have no enzyme, they may have the most severe outcomes, and this can be fatal. If the child has an abnormal gene that causes him/her to have some enzyme left, they may have more positive outcomes. Symptoms of SCAD can begin in infancy or during adulthood. When symptoms start in the first few days of life, (neonatal form), the disease is likely to be more severe than if the symptoms start during adulthood (adult-onset form). Depending on the severity, life expectancy can range from shortened to normal. There is great hope that enzyme replacement and gene therapies will be available in the future to alleviate symptoms and cure SCAD.

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

Save Babies Through Screening Foundation
This site provides a nice review of SCAD as well as links to other helpful websites and support groups. There is also a link to find out what diseases your state screens for.

United Mitochondrial Disease Foundation
A detailed website about mitochondrial disease including information on specific disease, ongoing clinical trials and research, and access to support.

Google Search for Short Chain Acyl CoA Dehydrogenase Deficiency (SCA

References and Sources

www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?201470 OMIM #201470 , SHORT-CHAIN ACYL-CoA DEHYDROGENASE DEFICIENCY