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Autosomal Recessive Ataxia Due to Ubiquinone Deficiency

MONDO:0012784 Curated 2026-07-04T00:00:00Z 9 harmonized findings

falcon · 15 citations openscientist · 24 citations

Concordant asserts the finding Partial supports a weaker/qualified form Contradictory conflicts with it Silent does not address it

Harmonized findings

The disorder is caused by biallelic (recessive) loss-of-function variants in COQ8A (formerly ADCK3/CABC1) and represents the most frequent form of primary coenzyme Q10 deficiency, clinically labeled COQ10D4 / ARCA2 / SCAR9 (OMIM 612016).

UNANIMOUS INTEGRATED

genetic_factor

Provider	Stance	Score	Evidence
falcon	CONCORDANT	90%	COQ8A (synonyms: ADCK3, CABC1) is the main causal gene referenced for the ataxia phenotype. Falcon names COQ8A (ADCK3/CABC1) as the causal gene and, in its identifier section, ties it to COQ10D4/ARCA2/SCAR9 and OMIM 612016. DOI:10.3390/metabo12100955, DOI:10.1186/s13041-022-00900-3
openscientist	CONCORDANT	95%	the most frequent form of hereditary CoQ10 deficiency (Q10 deficiency-4 OMIM #612016) which is mainly associated with autosomal recessive spinocerebellar ataxia (ARCA2, SCAR9) OpenScientist states the same gene and disease identity, adding that it is the most frequent hereditary CoQ10 deficiency and mapping ARCA2/SCAR9/OMIM 612016. PMID:30968303

Loss of COQ8A destabilizes coenzyme Q10 biosynthesis; the resulting CoQ10 deficiency impairs mitochondrial electron transport and oxidative phosphorylation and increases oxidative stress, causing preferential cerebellar (Purkinje cell) neurodegeneration.

UNANIMOUS INTEGRATED

pathophysiology

Provider	Stance	Score	Evidence
falcon	CONCORDANT	90%	COQ8A dysfunction → reduced/abnormal CoQ10 homeostasis (ubiquinone/ubiquinol pool) → impaired electron transfer and oxidative phosphorylation + altered redox buffering → selective vulnerability of cerebellar circuitry (Purkinje system and dentate-related pathways) → progressive cerebellar syndrome (ataxia, dysarthria, tremor) ± multisystem features. Falcon lays out the same upstream-to-downstream causal chain from COQ8A dysfunction through OXPHOS failure to cerebellar/Purkinje vulnerability. DOI:10.3390/metabo12100955, DOI:10.1002/ana.25751
openscientist	CONCORDANT	95%	Since CoQ10 serves as the essential electron carrier between complexes I/II and complex III of the mitochondrial respiratory chain, its deficiency causes impaired oxidative phosphorylation, decreased ATP production, increased reactive oxygen species (ROS) generation, and oxidative stress, ultimately leading to neurodegeneration with preferential vulnerability of cerebellar Purkinje cells. OpenScientist gives the identical mechanistic chain with the added specific Complex II+III/ATP/ROS detail and Purkinje-cell vulnerability.

COQ8A is not a canonical protein kinase but an atypical ATPase that binds lipid CoQ intermediates and stabilizes the multi-subunit CoQ biosynthesis complex.

SINGLE LEAD

gene_function

Provider	Stance	Score	Evidence
openscientist	CONCORDANT	95%	Although COQ8 was predicted to be a protein kinase, we demonstrate that it lacks canonical protein kinase activity in trans. Instead, COQ8 has ATPase activity and interacts with lipid CoQ intermediates, functions that are likely conserved across all domains of life OpenScientist explicitly resolves the kinase-vs-ATPase question and details the stabilizing role of COQ8A in the CoQ synthome. PMID:27499294, PMID:25498144, PMID:26866375
falcon	SILENT	—	Falcon treats COQ8A only as a regulator of CoQ10 biosynthesis and never addresses its ATPase (vs kinase) molecular function or its role in the biosynthetic complex.

The core phenotype is childhood-onset, slowly progressive cerebellar ataxia with cerebellar atrophy on MRI, accompanied by a variable spectrum of epilepsy, cognitive impairment, movement disorders, and exercise intolerance.

UNANIMOUS INTEGRATED

phenotype

Provider	Stance	Score	Evidence
falcon	CONCORDANT	85%	the cohort reports cerebellar atrophy as universal and notes dentate/pontine T2 changes in a subset (28%). Falcon reports cerebellar atrophy as universal in the n=59 cohort and, in its phenotype section, lists epilepsy (32%), cognitive impairment (49%), exercise intolerance (25%), and hyperkinetic movement disorders (41%). DOI:10.1002/ana.25751
openscientist	CONCORDANT	90%	Clinical presentation is characterized by a variable degree of cerebellar atrophy and a broad spectrum of associated symptoms, including muscular involvement, movement disorders, neurosensory loss, cognitive impairment, psychiatric symptoms and epilepsy OpenScientist gives the same cerebellar-atrophy-plus-broad-spectrum phenotype and expands the multisystem list (psychiatric, neurosensory). PMID:33622667

The disease is ultra-rare; a firm prevalence has not been established, with only on the order of 100-150 cases reported worldwide.

MAJORITY LEAD

epidemiology

Provider	Stance	Score	Evidence
openscientist	CONCORDANT	85%	Unknown; estimated <1/1,000,000. This is an ultra-rare disease. OpenScientist quantifies the rarity as an estimated point prevalence below 1 per 1,000,000 with ~100-150 reported cases.
falcon	PARTIAL	50%	one review states that prevalence is unknown and summarizes reported cases internationally. Falcon agrees prevalence is unknown but does not commit to a rarity band (<1/1,000,000) or a case count, so it partially supports the finding. DOI:10.3390/metabo12100955

Coenzyme Q10 supplementation is the main disease-directed therapy and the condition is regarded as potentially treatable, but the clinical response is only partial, with roughly half of treated patients classified as responders.

UNANIMOUS INTEGRATED

treatmentprognosis

Provider	Stance	Score	Evidence
falcon	CONCORDANT	90%	13 of 30 patients (43%) were classified as responders, and 15 of 30 (50%) as nonresponders Falcon quantifies the partial-response reality from the multicenter cohort (43% responders, 50% nonresponders among treated patients). DOI:10.1002/ana.25751
openscientist	CONCORDANT	85%	only half of patients could got notable improvement in ataxia OpenScientist independently reports the ~50% response rate to CoQ10 supplementation, concordant with Falcon's cohort figure. PMID:38429489

Diagnosis rests on demonstrating tissue CoQ10 deficiency, with muscle CoQ10 measurement as the key biochemical test (serum/plasma CoQ10 may be normal), plus biallelic COQ8A variants confirmed by sequencing.

UNANIMOUS INTEGRATED

diagnosis

Provider	Stance	Score	Evidence
falcon	CONCORDANT	90%	measurement of ubiquinone in a muscle biopsy remains the gold standard test Falcon states muscle biopsy CoQ10 is the gold standard and warns that serum CoQ10 may be normal, matching the diagnostic emphasis on tissue measurement. DOI:10.3390/metabo12100955
openscientist	CONCORDANT	85%	Skeletal muscle biochemistry revealed decreased activities of complexes I+III and II+III and a severe reduction of CoQ10 OpenScientist likewise treats muscle CoQ10/respiratory-chain biochemistry as the diagnostic anchor and notes normal plasma levels do not exclude the diagnosis. PMID:26818466

The natural history is slowly progressive over years to decades, so early diagnosis and treatment are emphasized to limit irreversible neuronal damage.

UNANIMOUS INTEGRATED

prognosis

Provider	Stance	Score	Evidence
falcon	CONCORDANT	85%	Slow progression on SARA (~0.45/year) in longitudinal drug-naïve analysis. Falcon anchors the slow-progression claim with a quantitative SARA progression rate (~0.45 points/year) from the drug-naive longitudinal cohort. DOI:10.1002/ana.25751
openscientist	CONCORDANT	80%	Slowly progressive. Cerebellar ataxia worsens over years to decades. OpenScientist gives the same slowly-progressive natural history and stresses that early treatment timing appears critical.

Animal models recapitulate the disease, supporting the causal mechanism: Coq8/COQ8A loss produces neurodegeneration and locomotor/ataxic phenotypes across species.

MAJORITY LEAD

pathophysiologygene_function

Provider	Stance	Score	Evidence
openscientist	CONCORDANT	90%	Mice lacking COQ8A develop a slowly progressive cerebellar ataxia linked to Purkinje cell dysfunction and mild exercise intolerance, recapitulating ARCA2 OpenScientist cites the Coq8a knockout mouse that reproduces progressive cerebellar ataxia and Purkinje-cell dysfunction, plus the Drosophila model. PMID:27499294, PMID:35139868
falcon	PARTIAL	50%	the model showed locomotor deficits and photoreceptor degeneration with Coq8 knockdown. Falcon supplies only the Drosophila Coq8 model (locomotor deficits, photoreceptor degeneration) and does not report the mammalian Coq8a knockout that recapitulates the cerebellar ataxia, so it partially supports the claim. DOI:10.1186/s13041-022-00900-3

Narrative

Overview

Both providers frame Autosomal Recessive Ataxia Due to Ubiquinone Deficiency as COQ8A-related primary coenzyme Q10 deficiency (COQ10D4 / ARCA2 / SCAR9, OMIM 612016): a recessive, potentially treatable mitochondrial disorder in which biallelic COQ8A loss impairs CoQ10 biosynthesis, degrades oxidative phosphorylation, and drives progressive cerebellar (Purkinje cell) neurodegeneration. Falcon is cohort/treatment-response focused (leaning on the n=59 multicenter study), while OpenScientist is broader and more mechanistic, adding molecular-function, model-organism, and diagnostic detail.

Agreement

The reports converge on the essentials: the COQ8A/ADCK3 genetic cause and disease identity; the CoQ10-deficiency-to-OXPHOS-failure-to-cerebellar- degeneration causal chain; the childhood-onset cerebellar ataxia with (near-)universal cerebellar atrophy and a variable epilepsy/cognitive/ movement-disorder spectrum; muscle CoQ10 as the key diagnostic measurement; slow progression with an emphasis on early treatment; and CoQ10 supplementation as the main therapy with only ~50% of patients responding.

Divergence

OpenScientist contributes material Falcon does not: the resolution of COQ8A as an atypical ATPase (not a canonical kinase) that stabilizes the CoQ synthome, a quantified ultra-rare prevalence band (<1/1,000,000), and the mammalian Coq8a-knockout mouse that recapitulates ARCA2. Falcon covers only the Drosophila model and leaves prevalence as "unknown" without a rarity band. These are differences of coverage and specificity, not conflicts — no genuine contradiction was found between the two reports.

Integration

The convergent core (COQ8A cause, CoQ10-deficiency mechanism, cerebellar phenotype with atrophy, muscle-CoQ10 diagnosis, slow progression, and partial CoQ10-supplementation response) supports the existing kb/disorders/Autosomal_Recessive_Ataxia_Due_to_Ubiquinone_Deficiency.yaml pathophysiology, phenotype, diagnosis, and treatment nodes.

Not integrated (leads)

The COQ8A ATPase molecular-function detail, the ultra-rare prevalence estimate, and the animal-model recapitulation are retained as research leads pending verification of the underlying primary literature before promotion to curated evidence.

Cross-provider synthesis comparing the falcon (Edison Scientific Literature, cohort/treatment-focused) and openscientist (autonomous, comprehensive) reports. best_matching_text values are verbatim excerpts from the respective report files; literature evidence snippets and ontology terms are intentionally left to the main curation pipeline on the disorder YAML. No direct contradictions were identified; divergence is coverage/specificity (OpenScientist adds ATPase molecular function, a quantified prevalence band, and the Coq8a knockout mouse).