Neuroacanthocytosis refers to a group of genetic disorders that give rise to movement disorders, neurological deficits and abnormally shaped red blood cells (acanthocytosis).
These conditions mainly affect the basal ganglia of the brain, which is responsible for the regulation of movement.
Neuroacanthocytosis can be subdivided into four syndromes as follows:
- Huntington’s disease-like 2 (mutation of JPH3 gene and autosomal dominant inheritance)
- McLeod syndrome (mutation of XK gene on X-chromosome and X-linked recessive inheritance)
- Chorea acanthocytosis (mutation of VPS13A CHAC gene and autosomal recessive inheritance)
- Pantothenate kinase-associated neurodegeneration (mutation of PKAN2 gene and autosomal recessive inheritance)
These disorders arise from different genetic mutations and symptoms vary between the conditions. However, typical symptoms that are observed across all of the conditions include the following.
- Chorea – This is the most common movement disorder associated with neuroacanthocytosis. Chorea describes involuntary, rapid movements of the body, particularly the face, hands and feet. Tongue and lip biting are also common.
- Parkinsonism or slowness of movement.
- Dystonia or abnormal body posture
- Problems walking
- Muscle weakness
- Cognitive impairment
- Psychiatric symptoms
- On analysis, red blood cells are typically spiculated, with a spur shaped cell membrane. These cells are called acanthocytes, after which the disease is named. Acanthocytosis is not always seen in HDL2 and PKAN.
- Difficulty speaking and eating
- Cardiac problems are typical in people with McLeod syndrome
There is some disagreement among experts regarding which disorders should be included under the umbrella of neuroacanthocytosis. In some literature, the conditions abetalipoproteinemia and hypobetalipoproteinemia types 1 and 2 are included as types of neuroacanthocytosis.
Symptom onset usually occurs between the age of 20 and 40 years, although symptoms can start as early on as 10 years of age. Huntington's disease-like 2 is marginally more common among South Africans than among other ethnicities and McLeod Syndrome is more common among males than females.
Neuroacanthocytosis is usually diagnosed based on symptoms, clinical observations, family history, imaging studies and laboratory investigations.
At present, there is no treatment available to cure this condition or slow its progression. Treatment is therefore supportive and focused on alleviating symptoms.
Antipsychotic medications that block dopamine may be used to decrease involuntary movements and ease psychotic symptoms. Botulinum toxin has been shown to improve dystonia. Individuals who are having difficulty eating may benefit from the use of a feeding tube to help prevent them becoming malnourished. Anticonvulsants may be used to treat seizures and some individuals may benefit from the use of antidepressants. Occupational therapy, speech therapy and physical therapy may also be beneficial.
These degenerative diseases are progressive, with most people eventually dying due to cardiac or neurological complications.
The National Institute of Neurological Disorders and Stroke (NINDS) supports research into conditions such as neuroacanthocytosis.
The research is aimed at improving knowledge and understanding about such disorders and potential therapies for treating them. Some of the genetic mutations involved in causing certain forms of neuroacanthocytosis have been identified and research into the involvement of the basal ganglia is also being conducted. Researchers hope to find associations between some of the genetic mutations identified and characteristic features of these disease.
Other research is focused on what causes the sudden death that sometimes occurs in those who develop heart muscle abnormalities as a complication of the diseases.