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Autosomal recessive spinocerebellar ataxia 20(SCAR20)

MedGen UID:
1684324
Concept ID:
C5190595
Disease or Syndrome
Synonyms: SCAR20; SPINOCEREBELLAR ATAXIA, AUTOSOMAL RECESSIVE 20
SNOMED CT: Intellectual disability, coarse face, macrocephaly, cerebellar hypotrophy syndrome (782753000); SCAR20 - autosomal recessive spinocerebellar ataxia type 20 (782753000); Autosomal recessive spinocerebellar ataxia type 20 (782753000)
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
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 individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
 
Gene (location): SNX14 (6q14.3)
 
Monarch Initiative: MONDO:0014601
OMIM®: 616354
Orphanet: ORPHA397709

Definition

Autosomal recessive spinocerebellar ataxia-20 is a neurodevelopmental disorder characterized by severely delayed psychomotor development with poor or absent speech, wide-based or absent gait, coarse facies, and cerebellar atrophy (summary by Thomas et al., 2014). [from OMIM]

Clinical features

From HPO
Oligosacchariduria
MedGen UID:
869388
Concept ID:
C4023815
Finding
Increased urinary excretion of oligosaccharides (low molecular weight carbohydrate chains composed of at least three monosaccharide subunits), derived from a partial degradation of glycoproteins.
Clubfoot
MedGen UID:
3130
Concept ID:
C0009081
Congenital Abnormality
Clubfoot is a congenital limb deformity defined as fixation of the foot in cavus, adductus, varus, and equinus (i.e., inclined inwards, axially rotated outwards, and pointing downwards) with concomitant soft tissue abnormalities (Cardy et al., 2007). Clubfoot may occur in isolation or as part of a syndrome (e.g., diastrophic dysplasia, 222600). Clubfoot has been reported with deficiency of long bones and mirror-image polydactyly (Gurnett et al., 2008; Klopocki et al., 2012).
Brachydactyly
MedGen UID:
67454
Concept ID:
C0221357
Congenital Abnormality
Digits that appear disproportionately short compared to the hand/foot. The word brachydactyly is used here to describe a series distinct patterns of shortened digits (brachydactyly types A-E). This is the sense used here.
Clinodactyly
MedGen UID:
1644094
Concept ID:
C4551485
Congenital Abnormality
An angulation of a digit at an interphalangeal joint in the plane of the palm (finger) or sole (toe).
Hepatomegaly
MedGen UID:
42428
Concept ID:
C0019209
Finding
Abnormally increased size of the liver.
Sensorineural hearing loss disorder
MedGen UID:
9164
Concept ID:
C0018784
Disease or Syndrome
A type of hearing impairment in one or both ears related to an abnormal functionality of the cochlear nerve.
Hearing impairment
MedGen UID:
235586
Concept ID:
C1384666
Disease or Syndrome
A decreased magnitude of the sensory perception of sound.
Apraxia
MedGen UID:
8166
Concept ID:
C0003635
Mental or Behavioral Dysfunction
A defect in the understanding of complex motor commands and in the execution of certain learned movements, i.e., deficits in the cognitive components of learned movements.
Cerebellar ataxia
MedGen UID:
849
Concept ID:
C0007758
Disease or Syndrome
Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).
Spasticity
MedGen UID:
7753
Concept ID:
C0026838
Sign or Symptom
A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes.
Babinski sign
MedGen UID:
19708
Concept ID:
C0034935
Finding
Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract.
Seizure
MedGen UID:
20693
Concept ID:
C0036572
Sign or Symptom
A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
Cerebellar hypoplasia
MedGen UID:
120578
Concept ID:
C0266470
Congenital Abnormality
Cerebellar hypoplasia is a descriptive term implying a cerebellum with a reduced volume, but a normal shape and is stable over time.
Delayed speech and language development
MedGen UID:
105318
Concept ID:
C0454644
Finding
A degree of language development that is significantly below the norm for a child of a specified age.
Global developmental delay
MedGen UID:
107838
Concept ID:
C0557874
Finding
A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.
Inability to walk
MedGen UID:
107860
Concept ID:
C0560046
Finding
Incapability to ambulate.
Hyporeflexia
MedGen UID:
195967
Concept ID:
C0700078
Finding
Reduction of neurologic reflexes such as the knee-jerk reaction.
Cerebellar atrophy
MedGen UID:
196624
Concept ID:
C0740279
Disease or Syndrome
Cerebellar atrophy is defined as a cerebellum with initially normal structures, in a posterior fossa with normal size, which displays enlarged fissures (interfolial spaces) in comparison to the foliae secondary to loss of tissue. Cerebellar atrophy implies irreversible loss of tissue and result from an ongoing progressive disease until a final stage is reached or a single injury, e.g. an intoxication or infectious event.
Autistic behavior
MedGen UID:
163547
Concept ID:
C0856975
Mental or Behavioral Dysfunction
Persistent deficits in social interaction and communication and interaction as well as a markedly restricted repertoire of activity and interest as well as repetitive patterns of behavior.
Delayed gross motor development
MedGen UID:
332508
Concept ID:
C1837658
Finding
A type of motor delay characterized by a delay in acquiring the ability to control the large muscles of the body for walking, running, sitting, and crawling.
Absent speech
MedGen UID:
340737
Concept ID:
C1854882
Finding
Complete lack of development of speech and language abilities.
Intellectual disability
MedGen UID:
811461
Concept ID:
C3714756
Mental or Behavioral Dysfunction
Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70.
Delayed early-childhood social milestone development
MedGen UID:
868509
Concept ID:
C4022906
Finding
A failure to meet one or more age-related milestones of social behavior.
Delayed fine motor development
MedGen UID:
869257
Concept ID:
C4023681
Finding
A type of motor delay characterized by a delay in acquiring the ability to control the fingers and hands.
Delayed ability to sit
MedGen UID:
1368737
Concept ID:
C4476710
Finding
A failure to achieve the ability to sit at an appropriate developmental stage. Most children sit with support at 6 months of age and sit steadily without support at 9 months of age.
Cerebral cortical atrophy
MedGen UID:
1646740
Concept ID:
C4551583
Disease or Syndrome
Atrophy of the cortex of the cerebrum.
Hypotonia
MedGen UID:
10133
Concept ID:
C0026827
Finding
Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.
Scoliosis
MedGen UID:
11348
Concept ID:
C0036439
Disease or Syndrome
The presence of an abnormal lateral curvature of the spine.
Kyphoscoliosis
MedGen UID:
154361
Concept ID:
C0575158
Anatomical Abnormality
An abnormal curvature of the spine in both a coronal (lateral) and sagittal (back-to-front) plane.
Camptodactyly
MedGen UID:
195780
Concept ID:
C0685409
Congenital Abnormality
The distal interphalangeal joint and/or the proximal interphalangeal joint of the fingers or toes cannot be extended to 180 degrees by either active or passive extension.
Relative macrocephaly
MedGen UID:
338607
Concept ID:
C1849075
Congenital Abnormality
A relatively mild degree of macrocephaly in which the head circumference is not above two standard deviations from the mean, but appears dysproportionately large when other factors such as body stature are taken into account.
Splenomegaly
MedGen UID:
52469
Concept ID:
C0038002
Finding
Abnormal increased size of the spleen.
Macroglossia
MedGen UID:
44236
Concept ID:
C0024421
Disease or Syndrome
Increased length and width of the tongue.
Dental crowding
MedGen UID:
11850
Concept ID:
C0040433
Finding
Changes in alignment of teeth in the dental arch
Delayed eruption of teeth
MedGen UID:
68678
Concept ID:
C0239174
Finding
Delayed tooth eruption, which can be defined as tooth eruption more than 2 SD beyond the mean eruption age.
Bulbous nose
MedGen UID:
66013
Concept ID:
C0240543
Finding
Increased volume and globular shape of the anteroinferior aspect of the nose.
High palate
MedGen UID:
66814
Concept ID:
C0240635
Congenital Abnormality
Height of the palate more than 2 SD above the mean (objective) or palatal height at the level of the first permanent molar more than twice the height of the teeth (subjective).
Short palpebral fissure
MedGen UID:
98067
Concept ID:
C0423112
Finding
Distance between the medial and lateral canthi is more than 2 SD below the mean for age (objective); or, apparently reduced length of the palpebral fissures.
Epicanthus
MedGen UID:
151862
Concept ID:
C0678230
Congenital Abnormality
Epicanthus is a condition in which a fold of skin stretches from the upper to the lower eyelid, partially covering the inner canthus. Usher (1935) noted that epicanthus is a normal finding in the fetus of all races. Epicanthus also occurs in association with hereditary ptosis (110100).
Thick vermilion border
MedGen UID:
332232
Concept ID:
C1836543
Finding
Increased width of the skin of vermilion border region of upper lip.
Prominent forehead
MedGen UID:
373291
Concept ID:
C1837260
Finding
Forward prominence of the entire forehead, due to protrusion of the frontal bone.
Anteverted nares
MedGen UID:
326648
Concept ID:
C1840077
Finding
Anteriorly-facing nostrils viewed with the head in the Frankfurt horizontal and the eyes of the observer level with the eyes of the subject. This gives the appearance of an upturned nose (upturned nasal tip).
Coarse facial features
MedGen UID:
335284
Concept ID:
C1845847
Finding
Absence of fine and sharp appearance of brows, nose, lips, mouth, and chin, usually because of rounded and heavy features or thickened skin with or without thickening of subcutaneous and bony tissues.
Wide nasal base
MedGen UID:
341506
Concept ID:
C1849667
Finding
Increased distance between the attachments of the alae nasi to the face.
Broad philtrum
MedGen UID:
344210
Concept ID:
C1854111
Finding
Distance between the philtral ridges, measured just above the vermilion border, more than 2 standard deviations above the mean, or alternatively, an apparently increased distance between the ridges of the philtrum.
Broad face
MedGen UID:
349223
Concept ID:
C1859680
Finding
Bizygomatic (upper face) and bigonial (lower face) width greater than 2 standard deviations above the mean (objective); or an apparent increase in the width of the face (subjective).
Long philtrum
MedGen UID:
351278
Concept ID:
C1865014
Finding
Distance between nasal base and midline upper lip vermilion border more than 2 SD above the mean. Alternatively, an apparently increased distance between nasal base and midline upper lip vermilion border.
Hypertrichosis
MedGen UID:
43787
Concept ID:
C0020555
Disease or Syndrome
Hypertrichosis is increased hair growth that is abnormal in quantity or location.
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.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
  • CROGVAutosomal recessive spinocerebellar ataxia 20

Recent clinical studies

Etiology

Sait H, Moirangthem A, Agrawal V, Phadke SR
Am J Med Genet A 2022 Jun;188(6):1909-1914. Epub 2022 Feb 23 doi: 10.1002/ajmg.a.62701. PMID: 35195341
Ebrahimi-Fakhari D
Neuropediatrics 2018 Feb;49(1):18-25. Epub 2017 Nov 7 doi: 10.1055/s-0037-1608652. PMID: 29112993
Shukla A, Upadhyai P, Shah J, Neethukrishna K, Bielas S, Girisha KM
Eur J Med Genet 2017 Feb;60(2):118-123. Epub 2016 Nov 29 doi: 10.1016/j.ejmg.2016.11.006. PMID: 27913285Free PMC Article

Diagnosis

Sait H, Moirangthem A, Agrawal V, Phadke SR
Am J Med Genet A 2022 Jun;188(6):1909-1914. Epub 2022 Feb 23 doi: 10.1002/ajmg.a.62701. PMID: 35195341

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