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Spinocerebellar ataxia type 20(SCA20)

MedGen UID:
373352
•Concept ID:
C1837541
•
Disease or Syndrome
Synonyms: CHROMOSOME 11q12 DUPLICATION SYNDROME, 260-KB; SCA20; Spinocerebellar Ataxia Type20; SPINOCEREBELLAR ATAXIA WITH DYSPHONIA; SPINOCEREBELLAR ATAXIA WITH SPASMODIC COUGH
SNOMED CT: Spinocerebellar ataxia type 20 (718771009)
Modes of inheritance:
Autosomal dominant inheritance
MedGen UID:
141047
•Concept ID:
C0443147
•
Intellectual Product
Source: Orphanet
A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele.
Autosomal dominant inheritance (Orphanet)
 
Monarch Initiative: MONDO:0012098
OMIM®: 608687
Orphanet: ORPHA101110

Definition

Spinocerebellar ataxia type 20 (SCA20) is characterized by a slowly progressive ataxia and dysarthria. Approximately two thirds of those affected also display palatal tremor ("myoclonus") and/or abnormal phonation clinically resembling spasmodic adductor dysphonia. Dysarthria, which may be abrupt in onset, precedes the onset of ataxia in about two thirds of affected individuals, sometimes by a number of years. Hypermetric horizontal saccades (without nystagmus or disturbance of vestibulo-ocular reflex gain) are seen in about half of affected persons. Although minor pyramidal signs (brisk knee jerks, crossed adductor spread) may be seen, spasticity and extensor plantar responses are not. Cognition is normal. Clinical information is based on the findings in 16 personally examined affected members of a single Australian family of Anglo-Celtic descent. [from GeneReviews]

Additional description

From OMIM
SCA20 is an autosomal dominant adult-onset disorder characterized by dysarthria due to spasmodic dysphonia followed by slowly progressive ataxia (summary by Knight et al., 2004). For a general discussion of autosomal dominant spinocerebellar ataxia, see SCA1 (164400).  http://www.omim.org/entry/608687

Clinical features

From HPO
Dysarthria
MedGen UID:
8510
•Concept ID:
C0013362
•
Mental or Behavioral Dysfunction
Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed.
See: Feature record | Search on this feature
Palatal tremor
MedGen UID:
45286
•Concept ID:
C0030214
•
Sign or Symptom
Palatal tremor (PT) is an involuntary, rhythmic and oscillatory movement of the soft palate. PT is a rare type of tremor involving the soft palate. It can be unilateral or bilateral.
See: Feature record | Search on this feature
Abnormal pyramidal sign
MedGen UID:
68582
•Concept ID:
C0234132
•
Sign or Symptom
Functional neurological abnormalities related to dysfunction of the pyramidal tract.
See: Feature record | Search on this feature
Action tremor
MedGen UID:
65875
•Concept ID:
C0234376
•
Sign or Symptom
A tremor present when the limbs are active, either when outstretched in a certain position or throughout a voluntary movement.
See: Feature record | Search on this feature
Postural tremor
MedGen UID:
66696
•Concept ID:
C0234378
•
Sign or Symptom
A type of tremors that is triggered by holding a limb in a fixed position.
See: Feature record | Search on this feature
High pitched voice
MedGen UID:
66836
•Concept ID:
C0241703
•
Finding
An abnormal increase in the pitch (frequency) of the voice.
See: Feature record | Search on this feature
Limb ataxia
MedGen UID:
196692
•Concept ID:
C0750937
•
Finding
A kind of ataxia that affects movements of the extremities.
See: Feature record | Search on this feature
Gait ataxia
MedGen UID:
155642
•Concept ID:
C0751837
•
Sign or Symptom
A type of ataxia characterized by the impairment of the ability to coordinate the movements required for normal walking. Gait ataxia is characteirzed by a wide-based staggering gait with a tendency to fall.
See: Feature record | Search on this feature
Dysphonia
MedGen UID:
282893
•Concept ID:
C1527344
•
Mental or Behavioral Dysfunction
An impairment in the ability to produce voice sounds.
See: Feature record | Search on this feature
Nystagmus
MedGen UID:
45166
•Concept ID:
C0028738
•
Disease or Syndrome
Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.
See: Feature record | Search on this feature
Hypermetric saccades
MedGen UID:
140835
•Concept ID:
C0423083
•
Finding
A saccade that overshoots the target with the dynamic saccade.
See: Feature record | Search on this feature
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Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
  • CROGVSpinocerebellar ataxia type 20
Follow this link to review classifications for Spinocerebellar ataxia type 20 in Orphanet.

Recent clinical studies

Etiology

Dominantly inherited ataxia and dysphonia with dentate calcification: spinocerebellar ataxia type 20.
Knight MA, Gardner RJ, Bahlo M, Matsuura T, Dixon JA, Forrest SM, Storey E
Brain 2004 May;127(Pt 5):1172-81. Epub 2004 Mar 3 doi: 10.1093/brain/awh139. PMID: 14998916

Diagnosis

Spinocerebellar ataxia type 20.
Storey E, Gardner RJ
Handb Clin Neurol 2012;103:567-73. doi: 10.1016/B978-0-444-51892-7.00038-3. PMID: 21827916
Spinocerebellar ataxia type 20 is genetically distinct from spinocerebellar ataxia type 5.
Lorenzo DN, Forrest SM, Ikeda Y, Dick KA, Ranum LP, Knight MA
Neurology 2006 Dec 12;67(11):2084-5. doi: 10.1212/01.wnl.0000247662.05197.59. PMID: 17159129

Clinical prediction guides

Spinocerebellar ataxia type 20.
Storey E, Knight MA, Forrest SM, Gardner RJ
Cerebellum 2005;4(1):55-7. doi: 10.1080/14734220410019048. PMID: 15895561
Dominantly inherited ataxia and dysphonia with dentate calcification: spinocerebellar ataxia type 20.
Knight MA, Gardner RJ, Bahlo M, Matsuura T, Dixon JA, Forrest SM, Storey E
Brain 2004 May;127(Pt 5):1172-81. Epub 2004 Mar 3 doi: 10.1093/brain/awh139. PMID: 14998916

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