Worldwide, the prevalence of all<unk> s combined is estimated to be 2 to 6 in 100,000 people. A Norwegian study of more than 2.5 million people published in March 2009 has found an<unk>  prevalence rate of 7.4/100,000 of population – a higher rate, but in the same range as previous studies. No differences in rate relating to gender were found, and average age at onset was 24 years. In the United States,<unk>  is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health which means that the disorder affects less than 200,000 people in the US population.
Hereditary spastic paraplegia
Spinal muscular atrophy
Madras motor neuron disease
Tropical ataxic neuropathy
Spinal and bulbar muscular atrophy
Autosomal recessive cerebellar ataxia type 1
Distal hereditary motor neuronopathies
Congenital distal spinal muscular atrophy