Spinocerebellar Ataxia Type 28

DISEASE CHARACTERISTICS: Spinocerebellar ataxia type 28 (SCA28) is characterized by young-adult onset, slowly progressive gait and limb ataxia, dysarthria, hyperreflexia of the lower limbs, nystagmus, and ophthalmoparesis. The usual age at onset is early adulthood (24.4 ± 14.9 years); range is from age three to 60 years. The course of the disease is slowly progressive without impairment of functional autonomy even decades after onset. DIAGNOSIS/TESTING: No features of SCA28 are pathognomonic; therefore, diagnosis depends on molecular genetic testing of AFG3L2, the only gene in which mutations are known to cause SCA28. MANAGEMENT: Treatment of manifestations: Crutches (less often canes) and walkers; home adaptations (e.g., grab bars for the bathtub or shower chairs) as needed; speech/language therapy for those with dysarthria and swallowing difficulties; physical therapy can help with tasks such as eating, dressing, walking, and bathing. Surgery as needed for severe ptosis. Prevention of secondary complications: Psychological support; weight control to facilitate ambulation; thickened feeds or gastrostomy feedings to avoid aspiration pneumonia. Surveillance: Annual assessment to evaluate stability or progression of the cerebellar ataxia. Monitoring of speech and swallowing. Agents/circumstances to avoid: Alcohol consumption and sedatives such as benzodiazepines that may worsen gait ataxia and coordination. GENETIC COUNSELING: SCA28 is inherited in an autosomal dominant manner. Most individuals diagnosed with SCA28 have an affected parent; the proportion of cases caused by de novo mutations is unknown. Each child of an individual with SCA28 has a 50% risk of inheriting the mutation. No laboratories offering molecular genetic testing for prenatal diagnosis of SCA 28 caused by mutation of AFG3L2 are listed in the GeneTests Laboratory Directory; however, for families in which the disease-causing mutation has been identified prenatal testing may be available from laboratories offering custom prenatal testing.