Krabbe Disease is a very rare and inherited metabolic disorder which destroys body and brain cells by the accumulation of harmful amounts of fatty oils and waxes. Also known as globoid cell leukodystrophy or galactosylceramide lipidosis and is caused by mutations in the GALC gene located on chromosome 14.
In some rare cases Krabbe disease may be caused by a lack of active saposin A. The condition is often fatal and affects the myelin sheath of the nervous system. It is a form of sphingolipidosis because it involves dysfunctional metabolism of sphingolipids. The disease is most often seen in infants and begins before age six months but can also occur during adolescence and adulthood. Krabbe disease is named after the Danish neurologist Knud Krabbe. Illinois, Kentucky, and Pennsylvania have laws to test for Krabbe and other diseases at birth.
The most common symptoms include severe deterioration of mental and motor skills, myoclonic seizures (shock-like contractions of the limbs suddenly), muscle weakness, hypertonia (inability of a muscle to stretch), deafness, optic atrophy, blindness, paralysis, optic nerve enlargement, difficulty swallowing, and spasticity (involuntary and awkward movement).
Krabbe disease is a genetic disease, caused when a child receives a defective or mutated gene from each parent. A gene supplies instructions for the development of specified proteins. Where Krabbe disease is concerned, the mutated genes interfere with the body’s ability to produce an enzyme called galactocerebrosidase (GALC). The limited supply of galactocerebrosidase means that lysosome won’t be properly broken down during the cell recycling process. This, in turn, causes galactolipids (fats) to accumulate. Normal levels of galactolipids serve as a protective coating for myelin (nerve cells), but, when these fats are over-produced, they damage the nerve cells they were intended to protect.
In some cases, only one defective gene is passed to a child, either from the mother or the father. When this happens, the child won’t develop Krabbe disease, but they will be a carrier. When one parent is a carrier of the disease, there remains a 50% chance that the child will also be a carrier, though there’s a 0% likelihood that they will get the disease. Where both parents are carriers, there’s a 25% chance each one of their children will be carriers and a 50% chance that each child will develop the disease.
While there is no known cure for Krabbe disease bone marrow transplantation has been shown to aid cases early in the course of the disease. Physical therapy may help to increase or maintain muscle tone and circulation. Cord blood transplants have proven successful in halting the disease as long as they are administered before noticeable symptoms appearing.
Since Krabbe disease is a genetic disorder, there’s no way to prevent a child from contracting the illness. When a couple is aware of a family history of Krabbe disease, they should consult a genetic counselor about the possibility of their children being born with the condition, prior to getting pregnant. Prenatal testing can identify the gene mutations responsible for Krabbe disease, but couples should be aware that there are risks associated with testing, including the chance of a miscarriage.
In treating Krabbe disease after the birth of the child, or when an individual develops the condition later in life, bone marrow and stem cell transplants have proven to be the most effective treatments. Additionally, physical therapy and occupational therapy can help to control and manage some symptoms.