Krabbe Disease
Patient Information
Characteristics
Background and History
This disorder was described by a Danish neurologist Knud Haraldsen Krabbe in 1916. It is primarily a disease of the white matter in the brain but involves nerves throughout the body.
Clinical Correlations
There is considerable variability of clinical disease among patients, even within families. It has been divided into at least four groups based on age of onset: infantile, late infantile, juvenile, and adult. The most severe form is found in infants who develop irritability and signs of delayed motor and mental development in the first 6 months of life. Unsteadiness with muscle stiffness and hyperactivity soon sets in followed by vision problems and weakness. Many infants do not live beyond a year of age. Other individuals, however, do not develop symptoms until late childhood or even adulthood but degeneration of the nervous system progresses rapidly.
Genetics
Inheritance
Krabbe disease is an autosomal recessive disorder with a horizontal family pattern. Parents who are usually clinically normal carriers have a 25% risk of having another child with the same disease for each pregnancy.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
The diagnosis is based on the neurological features as well as progression of the disorder and often it is the pediatrician or a neurologist who identifies the condition. A nerve conduction study or an MRI can help confirm the diagnosis. Treatment is experimental at this time but some improvement in the neurological symptoms may follow stem cell or cord blood infusions. This is most effective if applied in infancy before major symptoms occur.
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