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NA - Diseases - ChAc -

Disease characteristics

Chorea-acanthocytosis (ChAc) is characterized by a progressive movement disorder, a myopathy that can be subclinical, cognitive and behavior changes, and acanthocytosis of the red blood cells. The movement disorder is mostly limb chorea, but some individuals present with a parkinsonian syndrome. Dystonia is common and affects the oral region and the tongue in particular, causing dysarthria and serious dysphagia with resultant weight loss. Habitual tongue and lip biting are characteristic. Progressive cognitive and behavioral changes resemble those in a frontal lobe syndrome. Seizures are observed in almost half of affected individuals and can be the initial manifestation. Myopathy results in progressive distal muscle wasting and weakness. Mean age of onset in ChAc is about age 35 years, although ChAc can develop as early as the first decade or as late as the seventh decade. It runs a chronic progressive course and may lead to major disability within a few years. Life expectancy is reduced, with age of death ranging from 28 to 61 years.

Diagnosis and testing

The diagnosis of ChAc is based primarily on clinical findings, the presence of characteristic MRI findings, and evidence of muscle disease. CT and MRI reveal atrophy of the caudate nuclei with dilatation of the anterior horns of the lateral ventricles. MRI commonly shows T2-signal increase in the caudate and putamen. Acanthocytes are present in 5%-50% of the red cell population. In some cases, acanthocytosis may be absent or may appear only late in the course of the disease. Increased serum concentration of muscle creatine phosphokinase is observed in the majority of affected individuals. Muscle biopsy reveals central nuclei and atrophic fibers.  VPS13A, encoding chorein, is the only gene currently known to be associated with ChAc. Chorein detection are available free of charge on a research basis only (see documents for sampling information). VPS13A molecular genetic testing is available at a commercial basis from the MGZ, Munich, Germany.

Management

Treatment of ChAc may include: botulinum toxin for decreasing the oro-facio-bucco-lingual dystonia; feeding assistance; speech therapy; mechanical protective devices; splints for foot drop; phenytoin, clobazam, and valproate for seizure management; antidepressant or antipsychotic medications; dopamine antagonists such as atypical neuroleptics or tetrabenazine; and standard treatment for cardiomyopathy. Surveillance includes monitoring of nutritional status and adaptation of diet to assure adequate caloric intake, cardiac evaluations every five years, and EEG every third year.
 

Genetic counseling

ChAc is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Prenatal testing may be available through laboratories offering custom prenatal testing for families in which the disease-causing mutations have been identified in an affected family member.