← Research index  ·  Disorder page  ·  Source YAML

Cross-provider research synthesis

Autosomal Dominant Cerebellar Ataxia Type III

MONDO:0019793 Curated 2026-07-04T00:00:00Z 9 harmonized findings
falcon · 31 citations openscientist · 38 citations
Concordant asserts the finding Partial supports a weaker/qualified form Contradictory conflicts with it Silent does not address it

Harmonized findings

ADCA type III is Harding's clinicophenotypic class of autosomal dominant cerebellar ataxias defined by a pure or predominantly cerebellar syndrome with little or no extracerebellar involvement (only occasional pyramidal signs, ophthalmoplegia, or tremor).

UNANIMOUS INTEGRATED
phenotype
ProviderStanceScoreEvidence
falcon CONCORDANT 95% Autosomal Dominant Cerebellar Ataxia (ADCA) Type III is a type of spinocerebellar ataxia (SCA) classically characterized by pure cerebellar ataxia and occasionally by non-cerebellar signs such as pyramidal signs, ophthalmoplegia, and tremor.
Falcon quotes the Fujioka 2013 definition establishing ADCA III as a pure cerebellar SCA with only occasional extracerebellar signs.
DOI:10.1186/1750-1172-8-14
openscientist CONCORDANT 95% those that appear to elude neurological features outside of the cerebellum. At present 3 ADCA type III SCA genes have been published, SCA5, SCA6, and SCA14
OpenScientist independently frames ADCA III as the "pure" SCAs sparing extracerebellar systems, anchored to Harding's 1982 classification.
PMID:18418680

ADCA type III is genetically heterogeneous, encompassing several distinct SCA subtypes with predominant cerebellar involvement; the established causal genes include SPTBN2 (SCA5), CACNA1A (SCA6), TTBK2 (SCA11), and BEAN1/TK2 (SCA31), though the exact roster of included subtypes differs between sources.

UNANIMOUS INTEGRATED
genetic_factor
ProviderStanceScoreEvidence
falcon CONCORDANT 80% currently includes SCA5, SCA6, SCA11, SCA26, SCA30, SCA31
Falcon's roster is SCA5, SCA6, SCA11, SCA31 plus the mapped-only loci SCA26 and SCA30 (causal genes unestablished), and it omits SCA14.
DOI:10.1186/1750-1172-8-14
openscientist CONCORDANT 80% ADCA Type III encompasses several genetically distinct spinocerebellar ataxia (SCA) subtypes, most notably
OpenScientist names SCA5, SCA6, SCA11, SCA14 (PRKCG), and SCA31 — adding SCA14 that Falcon omits and dropping the mapped-only SCA26/SCA30 loci. Both agree on the four established genes; the composition of the class diverges.

SCA6 is caused by a small CAG (polyglutamine) repeat expansion in CACNA1A (P/Q-type voltage-gated calcium channel alpha-1A subunit), driving Purkinje cell dysfunction and degeneration.

UNANIMOUS INTEGRATED
pathophysiologygenetic_factor
ProviderStanceScoreEvidence
falcon CONCORDANT 90% CAG expansion in CACNA1A → expanded polyglutamine tract in CaV2.1 channel.
Falcon gives the CACNA1A CAG/polyQ trigger, proposing altered channel function and eventual neuronal death (framed as an older-review hypothesis of reduced Ca2+ influx).
DOI:10.1186/1750-1172-8-14
openscientist CONCORDANT 90% SCA6 is uniquely caused by a small CAG expansion (19–33 repeats; normal 4–18) in the last exon of
OpenScientist specifies the repeat ranges (19-33 vs normal 4-18, the smallest polyQ expansion) and, unlike Falcon, frames the channelopathy as excessive Ca2+ entry/excitotoxicity rather than reduced influx.
PMID:29427102

CACNA1A is bicistronic, additionally encoding the alpha-1ACT transcription factor, and SCA6 shows a distinctive pathology of non-ubiquitinated cytoplasmic polyglutamine aggregates in Purkinje cells (contrasting with the nuclear inclusions of other polyQ diseases).

SINGLE LEAD
gene_functionpathophysiology
ProviderStanceScoreEvidence
openscientist CONCORDANT 90% In SCA6 brains, numerous oval or rod-shaped aggregates were seen exclusively in the cytoplasm of Purkinje cells.
OpenScientist details the bicistronic alpha-1ACT transcription factor and the cytoplasmic, non-ubiquitinated aggregate pathology as a multi-layered pathogenesis (channelopathy + polyQ + transcriptional dysregulation).
PMID:29427102, PMID:10369863
falcon SILENT —
Falcon notes the polyglutamine tract but does not mention the bicistronic alpha-1ACT transcription factor or the non-ubiquitinated cytoplasmic Purkinje-cell aggregate pathology.

SCA31 is caused by a complex non-coding pentanucleotide repeat insertion containing (TGGAA)n in a BEAN1/TK2 shared intron, causing disease through RNA toxicity (nuclear repeat-RNA foci in Purkinje cells) and showing a strong Japanese founder effect.

UNANIMOUS INTEGRATED
pathophysiologygenetic_factorepidemiology
ProviderStanceScoreEvidence
falcon CONCORDANT 85% overexpression of (UGGAA)n repeat RNA causes toxicity and degeneration; co-expression of RNA-binding proteins (e.g., TDP-43) mitigates toxicity
Falcon describes the (TGGAA)n/(UGGAA)n repeat-RNA toxicity with RNA foci in Purkinje cell nuclei and the strong Japanese founder effect, supported by Drosophila RNA-chaperone rescue data.
DOI:10.1038/s10038-022-01091-4
openscientist CONCORDANT 90% SCA31 is caused by a 2.5–3.8 kb complex pentanucleotide repeat insertion containing (TGGAA)n, (TAGAA)n, (TAAAA)n, and (TAAAATAGAA)n in an intron shared by
OpenScientist specifies the 2.5-3.8 kb pentanucleotide insertion, the (UGGAA)n nuclear RNA foci mechanism, and the strong founder effect making the disease essentially absent outside Japan.
PMID:23607545, PMID:36319738

SCA5 results from SPTBN2 (beta-III spectrin) dysfunction that destabilizes Purkinje-cell membrane proteins such as the glutamate transporter EAAT4, disrupting glutamatergic homeostasis and Purkinje firing.

UNANIMOUS INTEGRATED
pathophysiologygenetic_factor
ProviderStanceScoreEvidence
falcon CONCORDANT 90% impaired stabilization/trafficking of glutamate transporter EAAT4, impaired axonal transport, reduced Purkinje spontaneous firing and dysregulated glutamatergic neurotransmission → cerebellar motor dysfunction
Falcon gives the beta-III spectrin causal chain via impaired EAAT4 stabilization and altered Purkinje firing.
DOI:10.1186/1750-1172-8-14
openscientist CONCORDANT 85% β-III spectrin stabilizes membrane proteins (EAAT4, glutamate receptors) at the Purkinje cell dendritic membrane. Dominant mutations likely act through a dominant-negative mechanism
OpenScientist agrees on beta-III spectrin's role stabilizing EAAT4 and adds an explicit dominant-negative mechanism for the heterozygous SCA5 mutations.
PMID:23236289

SCA11 is caused by truncating/frameshift TTBK2 (tau tubulin kinase 2) mutations acting largely through haploinsufficiency, disrupting ciliogenesis and microtubule dynamics in Purkinje cells.

UNANIMOUS INTEGRATED
genetic_factorpathophysiology
ProviderStanceScoreEvidence
falcon CONCORDANT 85% haploinsufficiency vs dominant-negative effects; reports of loss of kinase activity and mislocalization; and links to disrupted ciliogenesis
Falcon reports the TTBK2 truncating variants and the unresolved haploinsufficiency-vs-dominant-negative question, with links to disrupted ciliogenesis.
DOI:10.1007/s12311-023-01540-6
openscientist CONCORDANT 85% Truncating mutations likely cause disease through haploinsufficiency, disrupting ciliogenesis and microtubule dynamics in Purkinje cells
OpenScientist concurs that TTBK2 truncating mutations act through haploinsufficiency and disrupt ciliogenesis/microtubule dynamics.
PMID:20667868

Despite divergent molecular triggers across subtypes, ADCA type III converges on a shared downstream pathology of selective Purkinje cell dysfunction and degeneration, cerebellar cortical atrophy, and progressive cerebellar ataxia.

UNANIMOUS INTEGRATED
pathophysiology
ProviderStanceScoreEvidence
falcon CONCORDANT 85% hereditary ataxias involve diverse molecular pathways (excitability/calcium homeostasis, proteostasis, mitochondrial dysfunction, inflammation), while ADCA type III subtypes often converge on
Falcon states that despite diverse molecular pathways the subtypes converge on Purkinje cell dysfunction/degeneration and cerebellar network impairment.
DOI:10.3390/cells13040319
openscientist CONCORDANT 90% The five known ADCA Type III subtypes share a common downstream pathology—selective Purkinje cell degeneration in the cerebellum—but arrive there through fundamentally different molecular mechanisms
OpenScientist frames the same convergent-pathology model and adds the insight that Purkinje cell dysfunction precedes cell death, defining a therapeutic window.

No disease-modifying therapy exists for ADCA type III; management is supportive and symptomatic, and intensive/aerobic rehabilitation can slow functional decline.

MAJORITY INTEGRATED
treatmentprognosis
ProviderStanceScoreEvidence
openscientist CONCORDANT 90% SARA scores were stable, indicating slower progression than the expected natural history, through year 6
OpenScientist asserts no FDA-approved disease-modifying therapy and provides longitudinal evidence that intensive rehabilitation and high-intensity aerobic training slow SARA progression.
PMID:40906249, PMID:40946705
falcon PARTIAL 45% Physical therapy, occupational therapy, speech therapy (dysarthria/swallowing) are recommended in modern inherited ataxia management reviews
Falcon endorses supportive rehabilitation and symptomatic drugs (acetazolamide, gabapentin, tandospirone) and flags emerging ASO/gene therapy, but does not claim that rehabilitation slows disease progression.
DOI:10.1007/s00415-022-11383-6

Narrative

Overview

Both providers frame Autosomal Dominant Cerebellar Ataxia Type III as Harding's (1982) clinicophenotypic class of "pure" autosomal dominant cerebellar ataxias — a genetically heterogeneous group of SCA subtypes whose shared endpoint is selective Purkinje cell degeneration and progressive cerebellar ataxia with minimal extracerebellar involvement. Falcon (pathophysiology-focused, Fujioka 2013-anchored) organizes the report around each SCA subtype and its molecular chain; OpenScientist is broader and more recent, adding iPSC and mouse-model mechanistic detail, epidemiology, diagnostics, and treatment evidence.

Agreement

The reports concur on the core definition, autosomal dominant inheritance, and the four established causal genes (SPTBN2/SCA5, CACNA1A/SCA6, TTBK2/SCA11, BEAN1-TK2/SCA31). They agree on subtype mechanisms: SCA6 CAG polyglutamine expansion in the CACNA1A P/Q-type calcium channel; SCA31 non-coding (TGGAA)n pentanucleotide-insertion RNA toxicity with a strong Japanese founder effect; SCA5 beta-III spectrin destabilization of EAAT4; and SCA11 TTBK2 haploinsufficiency disrupting ciliogenesis. Both converge on a unifying model in which divergent molecular triggers funnel into Purkinje cell dysfunction/degeneration, cerebellar cortical atrophy, and slowly progressive ataxia, and both agree there is no disease-modifying therapy.

Divergence

The providers differ on the roster of subtypes: Falcon includes the mapped-only loci SCA26 and SCA30 and omits SCA14, whereas OpenScientist adds SCA14 (PRKCG) and drops SCA26/SCA30. On SCA6 channel biology they diverge in emphasis — Falcon cites an older hypothesis of reduced Ca2+ influx leading to neuronal death, while OpenScientist frames excessive Ca2+ entry and excitotoxicity, and only OpenScientist elaborates the bicistronic alpha-1ACT transcription factor and the non-ubiquitinated cytoplasmic Purkinje-cell aggregate pathology. OpenScientist contributes substantial unique content: patient iPSC Purkinje-cell findings (thyroid-hormone-dependent degeneration rescued by TRH/riluzole), pre-motor cognitive deficits in SCA6 mouse models, quantitative rehabilitation and aerobic-training trial data, and detailed diagnostic/epidemiology tables. The divergences are coverage/recency and framing, not direct factual contradictions.

Integration

The concordant subtype mechanisms (SCA5/SPTBN2, SCA6/CACNA1A, SCA11/TTBK2, SCA31/BEAN1-TK2) and the convergent Purkinje-cell-degeneration pathway map onto existing pathophysiology anchors in kb/disorders/Autosomal_Dominant_Cerebellar_Ataxia_Type_III.yaml and are suitable for integration once PMIDs/DOIs are fetch-verified. The pure cerebellar phenotype (gait/limb ataxia, dysarthria, nystagmus, cerebellar atrophy) and autosomal dominant inheritance are supported by both providers.

Not integrated (leads)

Retained as leads rather than promoted: the SCA6 bicistronic alpha-1ACT and cytoplasmic-aggregate detail, the iPSC thyroid-hormone/TRH-riluzole rescue, the pre-motor cognitive/spatial-navigation phenotype from mouse models, and the specific rehabilitation/aerobic-training and symptomatic-drug trial results. These are single-provider (mostly OpenScientist) and depend on model-system or small-cohort evidence that needs primary-source verification before curation.

Cross-provider synthesis comparing the falcon and openscientist deep-research reports for ADCA type III. best_matching_text values are verbatim excerpts from the cited report files (whitespace-normalized). No direct contradictions were found; divergence is subtype-roster composition, SCA6 calcium-flux framing, and coverage/recency (OpenScientist adds iPSC/mouse-model mechanism, epidemiology, and rehabilitation-trial detail). Header MONDO is taken from the dismech disorder entry (MONDO:0019793); OpenScientist alternatively reported MONDO:0016560. Literature evidence snippets are intentionally left for the main curation pipeline pending fetch-reference verification.