Krabbe disease is an inherited disorder characterized by a deficiency of the enzyme galactocerebroside beta-galactosidase (i.e., galactosylcereamidase) and resulting in destruction of myelin (a fatty material that surrounds and insulates many of the nerves).
Alternative Names
Globoid cell leukodystrophy; Galactosylcerebrosidase deficiency; Galactosylcereamidase deficiency
Causes, incidence, and risk factors
Krabbe disease is inherited as an autosomal recessive trait. It has a higher incidence among people of Scandinavian descent, but it generally affects about 1 in 150,000 infants. Absence of the enzyme galactocerebroside beta-galactosidase causes increasing destruction of myelin . The end result is a progressive destruction of the nervous system. Krabbe disease, like many other storage diseases, has an early onset form and a late onset form. In the early form, symptoms begin in the first months of life with feeding problems and failure to thrive , unexplained fevers, and vomiting . Changes in muscle tone are frequent, and seizures may begin very early, and are severe. Visual and hearing losses are progressive. Affected children eventually assume a rigid unusual body position called decerebrate posturing. Death follows shortly thereafter, usually before the second year of life. The late onset form of the disease begins in late childhood or early adolescence . Visual problems progressing to blindness may be the first symptom. Gait disturbance ( ataxia ) and muscle rigidity lead to progressive disability.
Signs and tests
Examination of the retina may show optic atrophy. Abnormal posturing may be evident ( opisthotonos and decerebrate posturing) in late stages of the disorder. There may be signs of deafness . Tests:
Galactocerebroside beta-galactosidase levels (levels can be measured from the serum, white blood cells, chorionic villi, and fibroblasts) CSF total protein may be increased MRI of the head is the best test to reveal abnormal white matter of the brain CT of the head Nerve conduction velocity showing delayed nerve conduction and evidence of demyelination Presence of abnormal Globoid cells in biopsy tissue of the nervous system Genetic testing may be available for the glycosylceramidase gene (GALC)
Treatment
There is no specific treatment for Krabbe disease. Bone marrow transplantation (with its own risks) has been attempted in early stages of the disease. It is too early to know if the new bone marrow can fully restore the brain to health in the small number of patients who have had this treatment. In the future there may be 'enzyme replacement therapy', but it is in the early stages of development as of late 2001. Prevention, for example by prenatal or genetic testing, is available.
Support groups
United Leukodystrophy Foundation - (800) 728-5483
Expectations (prognosis)
The outcome is likely to be poor. For example, infantile-onset cases die before 2 years of age on average. Later onset cases have survived into adulthood with neurologic disease.
Complications
Progressive central nervous system degeneration occurs. Blindness, deafness, and severe disturbances of muscle tone can result. The disease is usually fatal.
Calling your health care provider
Call your health care provider if your child develops symptoms of this disorder. Seizures , loss of consciousness , or abnormal posturing may be emergency symptoms. Call a genetic counselor if there is a family history of Krabbe disease.
Prevention
Genetic counseling is recommended for prospective parents with a family history of Krabbe disease. Carrier states may be recognized by decreased galactocerebroside beta-galactosidase levels in their white blood cells or skin fibroblasts. Prenatal diagnosis is possible by measuring galactocerebroside beta-galactosidase levels in cultured amniotic fluid cells or from cultured chorionic villi cells.