Krabbe disease: A progressive degenerative disorder of the nervous system that involves the destruction of myelin, a fatty material that surrounds and insulates nerves. Most patients have the infantile form of Krabbe disease. During the first few months of life, they seem normal, but before 6 months of age, the signs of extreme irritability, spasticity, and developmental delay become evident. Neurological deterioration leads to death generally before age 2. Other forms of Krabbe disease have late infantile, juvenile, or adult age of onset. Krabbe disease is inherited in an autosomal recessive manner and is due to a mutation in the gene for galactosylceramidase (GALC), leading to the accumulation of galactocerebroside in tissues. Diagnosis is made by finding 5 percent or less of normal GALC activity. Prenatal diagnosis is feasible. Also known as galactocerebrosidase deficiency, GALC deficiency, and globoid cell leukodystrophy.