Chorea-acanthocytosis (ChAc, also called choreoacanthocytosis) is a rare hereditary

disease A disease is a particular abnormal condition that adversely affects the structure or function (biology), function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical condi ...

--evidence suggests that only 500 to 1,000 people worldwide have the condition. It is caused by a mutation in a gene that directs structural

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s in

red blood cell Red blood cells (RBCs), referred to as erythrocytes (, with -''cyte'' translated as 'cell' in modern usage) in academia and medical publishing, also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cel ...

s. It belongs to a group of four diseases characterized under the name

neuroacanthocytosis Neuroacanthocytosis is a label applied to several genetic neurological conditions in which the blood contains misshapen, spiculated red blood cells called acanthocytes. The 'core' neuroacanthocytosis syndromes, in which acanthocytes are a typi ...

. When a patient's blood is viewed under a microscope, some of the red blood cells appear thorny. These thorny cells are called

acanthocyte Acanthocyte (from the Greek word ἄκανθα ''acantha'', meaning 'thorn'), in biology and medicine, refers to an abnormal form of red blood cell that has a spiked cell membrane, due to thorny projections. A similar term is spur cells. Often ...

s. Other effects of the disease may include involuntary muscle movements, impaired balance and coordination,behavioral changes, memory problems,difficulty swallowing, speech difficulties, seizures, muscle weakness, personality changes,and

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

al degradation similar to

Huntington's disease Huntington's disease (HD), also known as Huntington's chorea, is an incurable neurodegenerative disease that is mostly Genetic disorder#Autosomal dominant, inherited. It typically presents as a triad of progressive psychiatric, cognitive, and ...

. The average age of onset of symptoms is 35 years. The disease is incurable and inevitably leads to premature death. Chorea-acanthocytosis is a very complex autosomal recessive adult-onset neurodegenerative disorder. It often shows itself as a mixed movement disorder, in which chorea, tics, dystonia and even parkinsonism may appear as a symptom. This disease is also characterized by the presence of a few different movement disorders including chorea, dystonia etc. Chorea-acanthocytosis is considered an

autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosome ...

recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and ...

disorder, although a few cases with autosomal dominant inheritance have been noted.

Signs and symptoms

There are multiple symptoms that can help this disease to be diagnosed, this disease is marked by the presence of acanthocytes in blood (these acanthocytes can sometimes be absent or even make a late appearance in the course of the disease.) and neurodegeneration causing a choreiform movement disorder. Another one of them would be that this disease should be considered in patients who have elevated levels of acanthocytes in a peripheral blood film. The serum creatine kinase is often elevated in the body of the people who are affected by this disease. Choreoacanthocytosis patients may have a "rubber man" appearance with truncal instability and sudden, violent trunk spasms. Patients develop generalized chorea and a minority of Choreoacanthocytosis patients develops Parkinsonism. In a least one third of patients, seizures, typically generalized, are the first manifestation of disease. Impairment of memory and executive functions is frequent, although not invariable. People afflicted by this disease also experience a loss of neurons. Loss of neurons is a hallmark of neurodegenerative diseases. Due to the generally non-regenerative nature of neuronal cells in the adult central nervous system, this results in an irreversible and fatal process of neurodegeneration. There is also the presence of several movement related disorders including chorea, dystonia and bradykinesia, one of the more incapacitating ones includes Truncal spasms.

Cause

Choreo-acanthocytosis is caused by a mutation in both copies of the gene '' VPS13A'', which codes for vacuolar protein sorting-associated protein 13A.

Diagnosis

Protein function tests that demonstrate a reduce in chorein levels and also genetic analysis can confirm the diagnosis given to a patient. For a disease like this it is often necessary to sample the blood of the patient on multiple occasions with a specific request given to the haematologist to examine the film for acanthocytes. Another point is that the diagnosis of the disease can be confirmed by the absence of chorein in the western blot of the erythrocyte membranes.

Treatment

The treatment to battle the disease chorea-acanthocytosis is completely symptomatic. For example, botulinum toxin injections can help to control orolingual dystonia.

Deep brain stimulation Deep brain stimulation (DBS) is a type of neurostimulation therapy in which an implantable pulse generator is stereotactic surgery, surgically implanted subcutaneous tissue, below the skin of the chest and connected by Lead (electronics), leads ...

is a treatment that has varied effects on the people suffering from the symptoms of this disease, for some it has helped in a large way and for other people it did not help whatsoever, it is more effective on specific symptoms of the disease. Patients with chorea-acanthocytosis should undergo a cardiac evaluation every five years to look for cardiomyopathy.

References

External links

GeneReviews/NCBI/NIH/UW entry on chorea-acanthocytosis
{{DEFAULTSORT:Chorea Acanthocytosis Rare diseases Autosomal recessive disorders