Autosomal dominant cerebellar ataxia type II

Autosomal dominant cerebellar ataxia type II (ADCA type II), also known as spinocerebellar ataxia with retinal degeneration, is a group of inherited neurodegenerative disorders characterized by progressive cerebellar ataxia accompanied by pigmentary macular dystrophy or retinal degeneration. This classification, originally proposed by Harding, distinguishes ADCA type II from other autosomal dominant cerebellar ataxias by the presence of visual impairment due to retinal involvement. The most well-known genetic subtype within this group is spinocerebellar ataxia type 7 (SCA7), which is caused by a CAG trinucleotide repeat expansion in the ATXN7 gene. The disease primarily affects the cerebellum and retina, but can also involve the brainstem, spinal cord, and peripheral nerves. Key clinical features include progressive gait and limb ataxia, dysarthria (slurred speech), dysphagia (difficulty swallowing), and progressive visual loss that can lead to blindness. Patients may also develop ophthalmoplegia (impaired eye movements), pyramidal signs such as spasticity and hyperreflexia, and in some cases slow saccades. The age of onset is variable, ranging from childhood to adulthood, and earlier onset is often associated with larger repeat expansions and more severe disease progression, a phenomenon known as genetic anticipation. There is currently no cure or disease-modifying treatment for ADCA type II. Management is supportive and multidisciplinary, involving physical therapy and rehabilitation to maintain mobility, speech therapy for dysarthria and dysphagia, and ophthalmological monitoring for progressive visual decline. Low-vision aids and assistive devices may help patients cope with visual impairment. Genetic counseling is recommended for affected families given the autosomal dominant inheritance pattern and the phenomenon of anticipation, particularly through paternal transmission.

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