The most prevalent diseases were: Friedreich's ataxia in 35% (n = 7), Niemann-Pick type C (NPC) in 15% (n = 3), and ataxia with oculomotor apraxia type 2 in 15% (n = 3).
In the case of recessive disease, a stepwise diagnostic work-up is recommended, including both biochemical markers and targeted genetic testing, particularly aimed at Friedreich's ataxia, ataxia telangiectasia, ataxia due to vitamin E deficiency, polymerase gamma gene (POLG gene, various mutations), autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) and ataxia with oculomotor apraxia (AOA) types 1 and 2.
Machado-Joseph disease (spinocerebellar ataxia type 3) (prevalence, 3.1 per 100,000 population), Friedreich ataxia (prevalence, 1.0 per 100,000 population), and ataxia with oculomotor apraxia (prevalence, 0.4 per 100,000 population) were the most frequent HCAs.
These diseases are due to mutations in specific genes, some of which have been identified, such as frataxin in Friedreich ataxia, alpha-tocopherol transfer protein in ataxia with vitamin E deficiency (AVED), aprataxin in ataxia with oculomotor apraxia (AOA1), and senataxin in ataxia with oculomotor apraxia (AOA2).