Krabbe disease

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Krabbe disease (also known as globoid cell leukodystrophy or galactosylceramide lipidosis) is a rare, often fatal degenerative disorder that affects the myelin sheath of the nervous system. It is a form of sphingolipidosis, as it involves dysfunctional metabolism of sphingolipids.

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.

Less commonly, onset of Krabbe disease can occur in childhood, adolescence, or adulthood (late-onset forms). Visual problems and walking difficulties are the most common initial symptoms in this form of the disorder, however, signs and symptoms vary considerably among affected individuals.

etiology

Mutations in the GALC gene cause Krabbe disease. These mutations cause a deficiency of the enzyme galactosylceramidase. This deficiency leads to a progressive loss of myelin that covers many nerves. Without myelin, nerves in the brain and other parts of the body cannot function properly, leading to the signs and symptoms of Krabbe disease.

diagnosis and screening:

Laboratory tests
A blood sample and small skin sample (biopsy) will be sent to a laboratory to assess the level of GALC enzyme activity. Very low or no GALC activity level may indicate Krabbe disease.

Although the results help a doctor make a diagnosis, they don’t provide evidence of how quickly the disease may progress. For example, very low GALC activity doesn’t always mean that the condition will advance rapidly.

Imaging tests
Your doctor may order one or more imaging tests that can detect the loss of myelin (demyelination) in affected regions of the brain. These may include:

Magnetic resonance imaging (MRI), a technology that uses radio waves and a magnetic field to produce detailed 3-D images
Computerized tomography (CT), a specialized X-ray technology that produces 2-D images
Nerve conduction study
A nerve conduction study assesses the rate at which nerves conduct a signal — essentially how quickly can they send a message. A special device measures the time it takes an electrical impulse to travel from one point on the body to another. When myelin is impaired, nerve conduction is slower.

Genetic testing
A genetic test may be done with a blood sample to confirm a diagnosis. There are variant forms of the mutated gene that results in Krabbe disease. The particular type of mutation may provide some clues regarding the expected course of the disease.

Newborn screening
In some states, a screening test for Krabbe disease is part of a standard set of assessments for newborns. The initial screening test measures GALC enzyme activity. If the enzyme activity is found to be low, follow-up GALC tests and genetic tests are conducted.

sources:

https://ghr.nlm.nih.gov/condition/krabbe-disease#diagnosis

http://www.mayoclinic.org/diseases-conditions/krabbe-disease/basics/tests-diagnosis/con-20029450

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