Chorea-acanthocytosis is a rare, inherited neurological disorder impacting the brain and red blood cells. This condition leads to distinctive involuntary movements and a range of other symptoms. Only an estimated 500 to 1,000 individuals worldwide are affected by this condition, highlighting its rarity.
Understanding Chorea-Acanthocytosis
Chorea-acanthocytosis is classified as a neuroacanthocytosis syndrome, characterized by neurological problems and abnormally shaped red blood cells. The term “chorea” refers to the involuntary, irregular, and jerky movements that are a prominent feature of the disorder. These movements can affect various parts of the body.
The “acanthocytosis” component describes the presence of acanthocytes, which are red blood cells with thorny, spiky projections on their surface. While these unusual red blood cells are a defining characteristic, the neurological symptoms, particularly the movement disorders, are often the most noticeable and disabling aspects of the condition. The average age of symptom onset is around 35 years, although it can vary.
Recognizing the Symptoms
Neurological manifestations often include progressive chorea. Individuals may also experience dystonia, characterized by sustained muscle contractions that can lead to twisting and repetitive movements or abnormal postures. Parkinsonism, involving slowness of movement and rigidity, can also develop.
Other neurological symptoms encompass seizures, which affect nearly half of all individuals with the condition. Cognitive decline is common, impacting memory, executive functions, and the ability to process new information. Psychiatric issues are frequently observed and may even be among the first signs, including personality changes, depression, anxiety, and obsessive-compulsive behaviors. Some patients may exhibit self-mutilating behaviors, such as biting their lips and tongue.
Beyond neurological issues, individuals may experience muscle weakness (myopathy) and nerve damage (peripheral neuropathy), leading to reduced sensation in the limbs. Difficulties with swallowing (dysphagia) and speech (dysarthria) are common, caused by involuntary muscle twitches in the tongue and throat. Heart problems can also occur.
Causes and Diagnostic Approaches
Chorea-acanthocytosis is an autosomal recessive disorder, meaning an individual must inherit two copies of the mutated gene, one from each parent, to develop the condition. The disorder is caused by mutations in the VPS13A gene, which provides instructions for making a protein called chorein. This protein is believed to be involved in various cellular processes, including protein trafficking and lipid metabolism.
Diagnosis typically begins with a thorough clinical evaluation, where a neurologist assesses the patient’s movement disorders and other presenting symptoms. Blood tests are then performed to identify acanthocytes on a peripheral blood smear, though their absence does not completely rule out the diagnosis. Elevated serum creatine kinase levels are also frequently observed.
Confirmation of chorea-acanthocytosis is achieved through genetic testing, which involves DNA analysis of the VPS13A gene to detect specific mutations. Brain imaging, such as magnetic resonance imaging (MRI), may be conducted to look for structural changes, particularly atrophy of the caudate nucleus and impaired striatal glucose metabolism. Nerve conduction studies can also be performed to evaluate nerve function.
Management and Support
Currently, there is no cure for chorea-acanthocytosis, so management focuses on alleviating symptoms and providing supportive care to improve quality of life. Medications are often prescribed to manage specific symptoms. For chorea and dystonia, drugs that modulate neurotransmitters in the brain may be used to help control involuntary movements. Psychiatric symptoms like depression, anxiety, and obsessive-compulsive disorder are addressed with appropriate medications and therapies. Anti-epileptic drugs are employed to manage seizures.
Physical therapy aims to improve movement, balance, and coordination, helping individuals maintain mobility for as long as possible. Occupational therapy assists with adapting daily living activities, such as dressing and eating, to accommodate motor difficulties. Speech therapy is important for addressing swallowing difficulties (dysphagia) and communication problems (dysarthria), potentially reducing the risk of aspiration pneumonia and improving speech clarity. Nutritional support, often involving a dietitian, helps manage weight loss and ensure adequate nutrient intake, especially when swallowing becomes challenging.
A multidisciplinary care team is highly beneficial for individuals with chorea-acanthocytosis. This team typically includes neurologists, psychiatrists, cardiologists, dietitians, and social workers, who collaborate to address the wide range of symptoms and complications. Psychological support is also a significant aspect of management, as the progressive nature of the disease can have a profound mental health impact on both patients and their families. Counseling, support groups, and family therapy can provide emotional support and coping strategies. As the disease progresses, adaptive strategies, such as using assistive devices or modifying the home environment, become important for maintaining independence and safety.