Tests and diagnosisBy Mayo Clinic staff
Your child's doctor will conduct a physical exam, evaluating signs and symptoms that may indicate Krabbe disease, and then conduct a number of diagnostic tests.
Your child's doctor will take a blood sample and obtain a skin sample (biopsy), and send both to a laboratory for analysis. There, a lab technician will measure the activity of the GALC enzyme. If GALC activity level is low, your child may have Krabbe disease.
Although the results of these tests can help the doctor make a diagnosis, they don't provide evidence of how quickly the disease may progress. For example, a very low GALC activity finding doesn't always mean that the condition will advance rapidly.
To confirm the diagnosis, your child's doctor will recommend one or more of the following tests:
- Imaging scans of the brain and head. This may involve a magnetic resonance imaging (MRI) or computerized tomography (CT) scan. An MRI scan uses magnetic signals to create images of the brain. It's the best test to detect any abnormality in the brain that could be associated with Krabbe disease. Even so, in the early stages of the disease, an MRI can appear normal. A CT scan is a computer-enhanced, high-resolution imaging technique that creates 2-D X-ray pictures of the head.
- Nerve conduction studies. These measure the velocity of impulses being sent through the nervous system. This test may involve electrically stimulating the nerves, and then measuring the time it takes the electrical impulse to travel from the stimulation site to the recording device. When myelin is impaired, the nerve conduction is slower.
- Eye examination. A doctor who specializes in eye care (ophthalmologist) examines the retina, looking for indications of visual deterioration.
- Genetic testing. This may be conducted to detect the genetic mutation or defect associated with Krabbe disease.
Before birth, a fetus can be screened for Krabbe disease. To do this, your doctor withdraws amniotic fluid surrounding the fetus using a needle. The cells in the amniotic fluid are examined in the lab. A prenatal diagnosis of Krabbe disease can be made by evaluating the activity of GALC enzymes found in these cells or by genetic mutation analysis.
Prenatal diagnosis is not for everyone. When a family has had a previously affected child, then looking for an enzyme deficiency or mutations may be feasible, but this is not recommended when there isn't a family history.
- Krabbe disease. Genetics Home Reference. http://ghr.nlm.nih.gov/condition/krabbe-disease. Accessed April 20, 2011.
- Krabbe disease information page. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/krabbe/krabbe.htm. Accessed April 20, 2011.
- Duffner PK. The long-term outcomes of presymptomatic infants transplanted for Krabbe disease. Genetics in Medicine. 2009;11:450.
- Ropper AH, et al. Inherited metabolic diseases of the nervous system. In: Ropper AH, et al. Adams and Victor's Principles of Neurology. 9th ed. New York, N.Y.: The McGraw-Hill Companies; 2009. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=54. Accessed March 3, 2011.
- Krabbe disease. United Leukodystrophy Foundation. http://www.ulf.org/types/krabbe.html. Accessed April 20, 2011.
- Sakai N. Pathogenesis of leukodystrophy for Krabbe disease: Molecular mechanism and clinical treatment. Brain & Development. 2009;31:485.
- Duffner PK, et al. Newborn screening for Krabbe disease: The New York state model. Pediatric Neurology. 2009;40:245.
- Kemper AR, et al. Weighing the evidence for newborn screening for early-infantile Krabbe disease. Genetics in Medicine. 2010;12:539.
- National newborn screening status report. National Newborn Screening and Genetics Resource Center. http://genes-r-us.uthscsa.edu/nbsdisorders.pdf. Accessed April 20, 2011.
- Wenger DA. Krabbe disease. In: Pagon RA, et al. GeneReviews. http://www.ncbi.nlm.nih.gov/books/NBK1238/. Accessed April 20, 2011.
- Renaud DL (expert opinion). Mayo Clinic, Rochester, Minn. May 3, 2011.