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Last edited on November 21, 2009 by Timothy C. Hain, MD, Chicago IL.
Friedreich's ataxia was thought to be the most common inherited ataxia, before FXTAS was discovered. Friedreichs is transmitted with autosomal recessive inheritance. It's estimated prevalence in European populations is 1 in 50,000. It is associated with a mutation that consists of unstable expansion of GAA repeats on chromosome 9. FA alleles are found in about 11.4% of apparently recessive and 5.2% of apparently sporadic patients (Moseley et al, 1998).
Onset of symptoms is usually before 20 years of age (15 +- 8). There is ataxia of all four limbs associated with cerebellar dysarthria, absent reflexes in the lower limbs, sensory loss and pyramidal signs. Hypertrophic concentric cardiomyopathy is found in a majority of patients. Skeletal deformities and abnormalities in glucose metabolism are common. Other associated findings may be facial dysmorphia, myoclonus, dystonia, postural tremor, supranuclear gaze paresis, and mental retardation. Abnormal auditory evoked responses are found in about 50% of patients, and the auditory neuropathy syndrome has been reported in this disease. Sensorineural hearing loss may occur. Temporal bones from patients with Freidreichs have shown spiral ganglion and Scarpa's ganglion cell degeneration (Merchant et al, 2001). In patients homozygous for GAA expansion, the mean time to wheelchair confinement averages 10.8 years, and the mean disease duration is 15+-9 years. (Cosee et al, 1999).
The pathology of Friedreichs is largely confined to the dorsal root ganglion. Cerebellar neurons are usually normal.
Little treatment is available other than supportive care. A recent trial of Idebenone, a free radical scavenger, resulted in modest reductions in cardiac hypertrophy (Mariotti et al, 2003).
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