Krabbe Disease Causes, Symptoms and Treatment

Krabbe disease is inherited in an autosomal recessive manner. If both parents are carriers, each child has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Each healthy sib of a proband has a 2/3 chance of being a carrier. For genetic counseling purposes, a carrier frequency of one in 150 may be used for the general population. Prenatal diagnosis is possible either by measurement of GALC enzyme activity or by molecular genetic testing if both disease-causing alleles in an affected family member are known. Causes Krabbe disease is caused by mutations in the GALC gene, which causes a deficiency of an enzyme called galactosylceramidase. The buildup of unmetabolized lipids affects the growth of the nerve's protective myelin sheath (the covering that insulates many nerves) and causes severe degeneration of mental and motor skills. As part of a group of disorders known as leukodystrophies, Krabbe disease results from the imperfect growth and development of myelin. Persons with this gene defect do not make enough of a substance called galactocerebroside beta-galactosidase (galactosylceramidase). The body needs this substance to make myelin, the material that surrounds and protects nerve fibers. Without it, myelin breaks down, brain cells die, and nerves in the brain and other body areas do not work properly. The cause of Krabbe disease is a deficiency in an enzyme called galactocerebrosidase (GALC), which is essential for the maintenance of myelin a fatty substance that insulates your nerve fibers. A child needs to inherit an abnormal gene from each parent to trigger the disorder. Passing on the genes occurs in an inheritance pattern called autosomal recessive. A defect in the GALC gene causes Krabbe disease. Persons with this gene defect do not make enough of a substance called galactocerebroside beta-galactosidase (galactosylceramidase). The body needs this substance to make myelin, the material that surrounds and protects nerve fibers. Without it, myelin breaks down, brain cells die, and nerves in the brain and other body areas do not work properly. Symptoms The symptoms of Krabbe disease usually begin before the age of 1 year (the infantile form). Initial signs and symptoms typically include irritability, muscle weakness, feeding difficulties, episodes of fever without any sign of infection, stiff posture, and slowed mental and physical development. As the disease progresses, muscles continue to weaken, affecting the infant's ability to move, chew, swallow, and breathe. Affected infants also experience vision loss and seizures. The cause of Krabbe disease is a deficiency in an enzyme called galactocerebrosidase (GALC), which is essential for the maintenance of myelin a fatty substance that insulates your nerve fibers. A child needs to inherit an abnormal gene from each parent to trigger the disorder. Passing on the genes occurs in an inheritance pattern called autosomal recessive. Specifically, Krabbe disease has been linked to a defect in chromosome 14. Treatment There is no cure for Krabb disease. Results of a very small clinical trial of patients with infantile Krabb disease found that children who received umbilical cord blood stem cells from unrelated donors prior to symptom onset developed with little neurological impairment. Results also showed that disease progression stabilized faster in patients who receive cord blood compared to those who receive adult bone marrow. Bone marrow transplantation has been shown to benefit mild cases early in the course of the disease. Generally, treatment for the disorder is symptomatic and supportive.