ASAH-1 Disorders (Farber Disease and SMA-PME)
What are ASAH-1 disorders?
ASAH-1 disorders, which include Farber disease and spinal muscular atrophy associated with progressive myoclonic epilepsy (SMA-PME), are conditions caused by the body not having enough of a specific enzyme called acid ceramidase. This enzyme breaks down a specific type of fat in the body, which is used to make energy and build protective layers around nerve cells. Without the proper amount of enzyme, fats can build up in certain organs including the liver and lungs as well as in muscles and bones. Symptoms of Farber disease include small fatty bumps under the skin, swollen joints, and a hoarse or weak cry at birth. There are seven types of Farber disease, which range in severity. Babies with Farber disease most often show signs and symptoms at birth or within the first year of life.
Although SMA-PE is also caused by the body not having enough of the enzyme acid ceramidase, the symptoms are different from Farber disease. Children with SMA-PE will have normal development for the first few years of life, but will then begin to experience muscle weakness which first causes difficulty walking, and later, breathing and swallowing problems. A few years after the muscle weakness develops, they begin to have seizures (epilepsy).
How common are ASAH-1 disorders?
ASAH-1 disorders affect about 1 in every 500,000 babies born each year.
What can be done for ASAH-1 disorders?
Although there is no cure for ASAH-1 disorders, identifying these conditions early (at or soon after birth) may lead to better treatment of symptoms and an improved quality of life. For some types of ASAH-1 disorders, stem cell transplant may improve some symptoms, while many of the other symptoms can be managed by a team of medical specialists.
How are ASAH-1 disorders inherited?
ASAH-1 disorders are caused by changes in the ASAH1 gene. They are recessive inherited conditions, which means that a person must inherit two altered copies of the ASAH1 gene, one from each parent, in order to have the disease. People who have only one copy of the altered ASAH1 gene are called carriers, and are not expected to have symptoms of the condition. If a baby is identified as a carrier for an ASAH-1 disorder through Eli screening, genetic counseling and additional testing in the parents is recommended.