Spinocerebellar Ataxia Type 10: From Amerindians to Latin Americans

Abstract

Autosomal dominant cerebellar ataxias, currently denominated spinocerebellar ataxias (SCAs), constitute a large, complex group of heterogeneous autosomal dominant degenerative diseases characterized by progressive degeneration of the cerebellum and its afferent and efferent connections [1, 2]. Other nervous system structures are usually affected, including the basal ganglia, brainstem nuclei, pyramidal tracts, and posterior column and anterior horn of the spinal cord, as well as the peripheral nerves. SCAs are clinically characterized by the presence of cerebellar gait, limb ataxia (with dysmetria, dysdiadochokinesia, intention tremor), scanning dysarthria, dysphagia, nystagmus, and ocular motility abnormalities, which may be accompanied by extracerebellar signs such as ophthalmoplegia, pyramidal signs, movement disorders (including parkinsonism, dystonia, myoclonus, and chorea), dementia, epilepsy, visual disorders (including pigmentary retinopathy), lower motor neuron disease, and peripheral neuropathy [1–4]. Magnetic resonance imaging has been useful to demonstrate cerebellar atrophy with or without brainstem and occasionally whole brain atrophy depending on the form of the SCA. The prevalence of SCAs differs widely, mainly according to the ethnic distribution in most areas of the world where it has been studied [1–4]. One epidemiological study from the Netherlands [5] erichsuggested that the prevalence of SCAs is 3/100,000 and another from Norway suggested it is 4.2/100,000 [6]. Approximately 36 distinct loci of SCAs have been recognized. Among them, SCA type 3 (or Machado–Joseph disease) is the commonest subtype of SCA in the world. SCA type 10 (SCA10) is a rare form of SCA, but it is the commonest SCA after SCA type 2 in Mexico and SCA type 3 in Brazil [1, 2].