Friedreich Ataxia 1
Patient Information
Characteristics
Background and History
This is an inherited progressive degeneration of nervous system structures with life-threatening signs and symptoms. It was first described in 1863 by Nikolaus Friedreich, a professor of medicine in Germany.
Clinical Correlations
The first symptoms usually occur before puberty with unsteadiness (ataxia) in gait and limbs. There is extensive degeneration of the nervous system both within the brain and in the spinal cord. Mobility is impaired and many patients require a wheelchair due to muscle weakness within 15 years of the onset of symptoms. Skeletal deformities such as scoliosis, hammer toes, and foot deformities (pes cavus) occur secondarily. Sensory changes such as impairment of vibratory and position sense are common. Virtually all patients have damage in the visual system although few have severe loss of vision and many remain asymptomatic. Some patients have difficulty swallowing. Speech becomes slurred and some hearing loss is noted by a minority of individuals.
The heart muscle may become weakened with thickening of the heart wall and irregular heartbeats are experienced by many patients. Heart failure is the most common cause of death which occurs at a mean age of about 36 years. Diabetes mellitus is seen in about one-fourth of individuals.
Genetics
Inheritance
This is an autosomal recessive disorder that requires 2 mutations in a pair of genes for the disorder to become evident. Parents who carry a single mutation are clinically normal but if both have the mutation, they have a 25% risk of transmitting Friedreich ataxia to each of their children.
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 usually made by a neurologist based primarily on the combination of signs and symptoms. Few individuals live beyond the age of 40 years. There is no specific treatment for this disease but speech and physical therapy can be helpful in slowing the progression of some of the symptoms. Marked curvature of the spine may require surgical correction.
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