, degenerative, genetic disease with multiple types, each of which could be considered a disease in its own right.
.
was identified in 1993 for a dominantly inherited type. It was called “Spinocerebellar ataxia type 1" (SCA1). Subsequently, as additional dominant genes were found they were called SCA2, SCA3, etc. Usually, the "type" number of "SCA" refers to the order in which the gene was found. At this time, there are at least 29 different gene mutations which have been found (not all listed).
Many SCAs below fall under the category of polyglutamine diseases, which are caused when a disease-associated protein (i.e. ataxin-1, ataxin-3, etc.) contains a glutamine repeat beyond a certain threshold. In most dominant polyglutamine diseases, the glutamine repeat threshold is approximately 35, except for SCA3 which is beyond 50. Polyglutamine diseases are also known as "CAG Triplet Repeat Disorders" because CAG is the codon which codes for the amino acid glutamine. Many prefer to refer to these also as polyQ diseases since "Q" is the one-letter reference for glutamine.
| SCA Type |
Average Onset
(Range in Years) |
Average Duration
(Range in Years) |
What the patient experiences |
Common origin |
Problems
with DNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
|
| SCA1 (ATXN1) |
4th decade
(<10 to >60) |
15 years
(10-35) |
Hypermetric saccades, slow saccades, upper motor neuron Upper motor neurons are motor neurons that originate in the motor region of the cerebral cortex or the brain stem and carry motor information down to the final common pathway, that is, any motor neurons that are not directly responsible for stimulating the target muscle...
(note: saccades relates to eye movement) |
|
CAG repeat In the study of DNA sequences, one can distinguish two main types of repeated sequence:*Tandem repeats:**Satellite DNA**Minisatellite**Microsatellite*Interspersed repeats:**SINEs...
, 6p (Ataxin 1Ataxin-1 is a protein that in humans is encoded by the ATXN1 gene.-Interactions:Ataxin 1 has been shown to interact with Glyceraldehyde 3-phosphate dehydrogenase, Coilin, USP7 and UBE2E1.-External links:*...
) |
| SCA2 (ATXN2 Ataxin-2 is a protein that in humans is encoded by the ATXN2 gene.-Further reading:-External Links:*...
) |
3rd - 4th decade
(<10 to >60) |
10 years
(1-30) |
Diminished velocity saccades
areflexia (absence of neurologic reflexes) |
CubaThe Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
|
CAG repeat In the study of DNA sequences, one can distinguish two main types of repeated sequence:*Tandem repeats:**Satellite DNA**Minisatellite**Microsatellite*Interspersed repeats:**SINEs...
, 12q |
| SCA3 (MJD) (ATXN3) |
4th decade
(10-70) |
10 years
(1-20) |
Also called Machado-Joseph disease Machado–Joseph disease or Spinocerebellar ataxia type 3 is a rare autosomal, dominantly inherited neurodegenerative disease that causes progressive cerebellar ataxia, which results in a lack of muscle control and coordination of the upper and lower extremities...
(MJD)
Gaze-evoked nystagmus (a rapid, involuntary, oscillatoryOscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...
motionIn physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...
of the eyeball)
upper motor neuronUpper motor neurons are motor neurons that originate in the motor region of the cerebral cortex or the brain stem and carry motor information down to the final common pathway, that is, any motor neurons that are not directly responsible for stimulating the target muscle...
slow saccades |
AzoresThe Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
(PortugalPortugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
) |
CAG repeat In the study of DNA sequences, one can distinguish two main types of repeated sequence:*Tandem repeats:**Satellite DNA**Minisatellite**Microsatellite*Interspersed repeats:**SINEs...
, 14q |
| SCA4 (PLEKHG4 Puratrophin-1 is a protein that in humans is encoded by the PLEKHG4 gene.-Further reading:...
) |
4th - 7th decade
(19-72) |
Decades |
areflexia (absence of neurologic reflexes) |
|
ChromosomeA chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
16q |
| SCA5 (SPTBN2 Spectrin beta chain, brain 2 is a protein that in humans is encoded by the SPTBN2 gene.-Interactions:SPTBN2 has been shown to interact with UNC13B, ACTR1A and Beta-actin.-Further reading:...
) |
3rd - 4th decade
(10-68) |
>25 years |
Pure cerebellarThe cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
|
|
ChromosomeA chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
11 |
| SCA6 Spinocerebellar ataxia type 6 is a rare, late-onset, autosomal dominant disorder, which, like other types of SCA, is characterized by dysarthria, oculomotor disorders, incontinence, peripheral neuropathy, and ataxia of gait, stance and the limbs due to cerebellar dysfunction. Unlike other types,...
(CACNA1A) |
5th - 6th decade
(19-71) |
>25 years |
Downbeating nystagmus, positional vertigo Vertigo is a type of dizziness, where there is a feeling of motion when one is stationary. The symptoms are due to a dysfunction of the vestibular system in the inner ear...
Symptoms can appear for the first time as late as 65 years old. |
|
CAG repeat In the study of DNA sequences, one can distinguish two main types of repeated sequence:*Tandem repeats:**Satellite DNA**Minisatellite**Microsatellite*Interspersed repeats:**SINEs...
, 19p
CalciumCalcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
channel geneA gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
|
| SCA7 (ATXN7) |
3rd - 4th decade
(0.5 - 60) |
20 years
(1-45; early onset correlates with shorter duration) |
Macular degenerationAge-related macular degeneration is a medical condition which usually affects older adults and results in a loss of vision in the center of the visual field because of damage to the retina. It occurs in “dry” and “wet” forms. It is a major cause of blindness and visual impairment in older adults...
, upper motor neuronUpper motor neurons are motor neurons that originate in the motor region of the cerebral cortex or the brain stem and carry motor information down to the final common pathway, that is, any motor neurons that are not directly responsible for stimulating the target muscle...
, slow saccades |
|
CAG repeat In the study of DNA sequences, one can distinguish two main types of repeated sequence:*Tandem repeats:**Satellite DNA**Minisatellite**Microsatellite*Interspersed repeats:**SINEs...
, 3p (Ataxin 7Ataxin 7 is a protein associated with both olivopontocerebellar atrophy type 3 and spinocerebellar ataxia type 7 .-External links:*...
) |
| SCA8 (IOSCA) |
39 yrs
(18-65) |
Normal lifespan |
Horizontal In geometry, physics, astronomy, geography, and related sciences, a plane is said to be horizontal at a given point if it is perpendicular to the gradient of the gravity field at that point— in other words, if apparent gravity makes a plumb bob hang perpendicular to the plane at that point.In...
nystagmus (a rapid, involuntary, oscillatoryOscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...
motion of the eyeball), instablility, lack of coordination |
|
CTG repeat In the study of DNA sequences, one can distinguish two main types of repeated sequence:*Tandem repeats:**Satellite DNA**Minisatellite**Microsatellite*Interspersed repeats:**SINEs...
, 13q |
| SCA10 (ATXN10 Ataxin-10 is a protein that in humans is encoded by the ATXN10 gene.- Clinical significance :The autosomal dominant cerebellar ataxias are a clinically and genetically heterogeneous group of disorders characterized by ataxia, dysarthria, dysmetria, and intention tremor...
) |
36 years |
9 years |
ataxia Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
, seizureAn epileptic seizure, occasionally referred to as a fit, is defined as a transient symptom of "abnormal excessive or synchronous neuronal activity in the brain". The outward effect can be as dramatic as a wild thrashing movement or as mild as a brief loss of awareness...
s |
MexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
|
ChromosomeA chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
22q linked
pentanucleotide repeatIn the study of DNA sequences, one can distinguish two main types of repeated sequence:*Tandem repeats:**Satellite DNA**Minisatellite**Microsatellite*Interspersed repeats:**SINEs...
|
| SCA11 |
30 yrs
(15-70) |
Normal lifespan |
Mild, remain ambulatory (able to walk about on one's own) |
|
15q |
| SCA12 (PPP2R2B Serine/threonine-protein phosphatase 2A 55 kDa regulatory subunit B beta isoform is an enzyme that in humans is encoded by the PPP2R2B gene.-External Links:* -Further reading:...
) |
33 yrs
(8-55) |
|
HeadIn anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....
and handA hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
tremorA tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving to-and-fro movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the...
,
akinesia (loss of normal motor function, resulting in impaired muscleMuscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
movement) |
|
CAG repeat In the study of DNA sequences, one can distinguish two main types of repeated sequence:*Tandem repeats:**Satellite DNA**Minisatellite**Microsatellite*Interspersed repeats:**SINEs...
, 5q |
| SCA13 Spinocerebellar ataxia type 13 is a rare autosomal dominant disorder, which, like other types of SCA, is characterized by dysarthria, nystagmus, and ataxia of gait, stance and the limbs due to cerebellar dysfunction. Patients with SCA13 also tend to present with epilepsy, an inability to run, and...
|
Childhood or adulthood depending on mutation |
Depending on KCNC3 Potassium voltage-gated channel, Shaw-related subfamily, member 3 also known as KCNC3 or Kv3.3 is a protein which in humans is encoded by the KCNC3.- Function :...
(a kind of gene) |
Mental retardation Mental retardation is a generalized disorder appearing before adulthood, characterized by significantly impaired cognitive functioning and deficits in two or more adaptive behaviors...
|
|
19q |
| SCA14 (PRKCG Protein kinase C gamma type is an enzyme that in humans is encoded by the PRKCG gene.-External Links:* -Further reading:...
) |
28 yrs
(12-42) |
Decades
(1-30) |
Myoclonus Myoclonus is brief, involuntary twitching of a muscle or a group of muscles. It describes a medical sign and, generally, is not a diagnosis of a disease. Brief twitches are perfectly normal. The myoclonic twitches are usually caused by sudden muscle contractions; they also can result from brief...
(a sudden twitchingMuscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten, or remain the same...
of muscleMuscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s or parts of muscles, without any rhythm or pattern, occurring in various brainThe brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
disorders) |
|
19q |
| SCA16 |
39 yrs
(20-66) |
1–40 years |
HeadIn anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....
and handA hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
tremorA tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving to-and-fro movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the...
|
|
8q |
SCA17 (TBPThe TATA-binding protein is a general transcription factor that binds specifically to a DNA sequence called the TATA box. This DNA sequence is found about 35 base pairs upstream of the transcription start site in some eukaryotic gene promoters...
) |
|
CAG repeat In the study of DNA sequences, one can distinguish two main types of repeated sequence:*Tandem repeats:**Satellite DNA**Minisatellite**Microsatellite*Interspersed repeats:**SINEs...
, 6q (TATA-binding protein) |
| SCA19, SCA22 |
|
|
Mild cerebellarThe cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
syndromeIn medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...
, dysarthriaDysarthria is a motor speech disorder resulting from neurological injury of the motor component of the motor-speech system and is characterized by poor articulation of phonemes...
|
|
|
| SCA25 |
1.5-39 yrs |
Unknown |
ataxia Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
with sensorySenses are physiological capacities of organisms that provide inputs for perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology , and philosophy of perception...
neuropathy, vomitingVomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
and gastrointestinalThe human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
painPain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
. |
|
2p |
| SCA27 |
15-20 yrs |
Unknown |
ataxia Ataxia is a neurological sign and symptom that consists of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of the parts of the nervous system that coordinate movement, such as the cerebellum...
with low cognition, dyskinesiasDyskinesia is a movement disorder which consists of effects including diminished voluntary movements and the presence of involuntary movements, similar to tics or choreia. Dyskinesia can be anything from a slight tremor of the hands to uncontrollable movement of, most commonly, the upper body but...
and tremorA tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving to-and-fro movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the...
. |
|
FGF14 13q34 |
Four X-linked types have been described , but only the first of these has so far been tied to a gene (SCAX1).
and often associated with poor coordination of hands, speech, and eye movements. Frequently,
occurs, and different ataxias are known to affect different regions within the cerebellum.
, SCA results in unsteady and clumsy motion of the body due to a failure of the fine coordination of
The symptoms of an ataxia vary with the specific type and with the individual patient. Generally, a person with ataxia retains full mental capacity but may progressively lose physical control.
locus. The hereditary ataxias can be inherited in an autosomal dominant, autosomal recessive, or X-linked manner.
There is no currently known cure for spinocerebellar ataxia, which is considered to be a progressive and irreversible disease, although not all types cause equally severe disability. Treatments are generally directed towards alleviating symptoms, not the disease itself. Typically, a person afflicted with this disease will eventually be unable to perform
The treatment of incoordination or ataxia mostly involves the use of adaptive devices to allow the individual to maintain the greatest degree of independence for as long as possible. Such devices may include a cane, crutches, walker, or
for those with impaired gait. Other devices are available to assist with writing, feeding, and self care if hand and arm coordination are impaired; and
exist to help those with impaired speech. Many patients with hereditary or idiopathic forms of ataxia have other symptoms in addition to ataxia. Medications or other therapies might be appropriate for some of these symptoms, which could include tremor, stiffness, depression, spasticity, and
s, among others. Both onset of initial symptoms and duration of disease are variable. If the disease is caused by a
trinucleotide repeat CAG expansion, a longer expansion may lead to an earlier onset and a more radical progression of clinical symptoms.