Friedreich's ataxia in Western Norway.

Friedreich's ataxia (FA) was investigated in Western Norway, an area comprising several isolated communities and with a population of 725,000 as at 1 January 1968. The prevalence of FA was estimated to be 1/100,000 in this population. An autosomal recessive mode of transmission appeared likely in all instances. The gene frequency was only 7-9.10 minus 5, but the consanguinity rate was high in the families observed. The mutation rate was relatively high at 1-6.10 minus 5. The clinical features displayed by the 10 examined patients agreed well with those observed by other investigators. Spinal and cerebellar ataxia dominated the clinical picture. In most cases signs of peripheral neuropathy were also observed. Epilepsy was seen in some cases, and also dementia. Unspecific neuropathy, defined according to a scoring system may represent disease manifestation in FA heterozygotes.