IOSCA is a difficult, progressive degenerative disease causing damage to the peripheral and central nervous system. All known 24 patients are Finnish. Initial symptoms include ataxia, athetosis, ophthalmoplegia, hearing disability and muscular hypotonia. Sensory axonal neuropathy and associated optic atrophy are typical of the disease, as well as primary hypergonadotropic hypogonadism in girls. The patients are progressively severely disabled from the age of approx. eighteen months. The pathogenesis is unknown and there is no curative treatment for the disease.