PubMed MCP isn't permitted; I'll use the shell and web search.

Cached the three core papers (Sanderson 2021, van der Welle 2021, Steel 2020); now reading them for exact quotes.

Now the van der Welle and Steel abstracts.

Fetching Monfrini review and the 2026 Nakamura paper.

Looking up remaining ontology terms (GO, CL, VPS41 gene ID) before writing the report.

Spinocerebellar Ataxia, Autosomal Recessive 29 (SCAR29; MONDO:0030312): research report

Causal gene: VPS41. VPS41 is a subunit of the HOPS complex, which is specific to HOPS and not shared with the related CORVET complex. The gene is at 7p14.1. OMIM lists the gene as 605485 and the disease as 619389. MONDO records VPS41 as the causal gene through the dismech stub. The same gene appears in the working branch name (curate-scar29-vps41) and in the stub's source_tags: mondo_causal_gene=VPS41. The OMIM numbers come from NCBI MedGen and were not checked against OMIM directly.

Evidence base. Every quote below is copied from a file in references_cache/, generated with just fetch-reference. These are the core sources:

I did not retrieve PMIDs for the three DOI-keyed papers. The DOI is a valid reference key in dismech.

1. Disease information

• Overview. SCAR29 is an autosomal recessive, progressive neurodevelopmental disorder. Its main features are cerebellar ataxia, hypotonia, dystonia, intellectual disability, nystagmus and cerebellar (especially vermian) atrophy. It is caused by biallelic VPS41 variants that impair the HOPS complex's role in endolysosomal and autophagosomal fusion.

  "All affected individuals presented with a progressive neurodevelopmental disorder consisting of cognitive impairment, cerebellar atrophy/hypoplasia, motor dysfunction with ataxia and dystonia, and nystagmus." (PMID:33764426)

• Identifiers.
• MONDO:0030312
• OMIM 619389 (disease) and 605485 (gene), per MedGen
• MedGen 1788435
• No disease-specific ICD-10 code; the nearest is G11.1 (early-onset cerebellar ataxia).
• No disease-specific Orphanet code was found.
• Synonyms (from the MONDO stub): SCAR29; Barakat-Van Ham-Kaya syndrome; neurodevelopmental disorder with hypotonia and cerebellar ataxia.
• Nosology. The disorder belongs to the proposed group "HOPS-associated neurological disorders (HOPSANDs)", together with VPS16 and VPS11 disease.

  "We propose to name this group of diseases HOPS-associated neurological disorders (HOPSANDs), which are mainly characterized by dystonic presentations." (DOI:10.1093/brain/awab161)

• Data type. Everything known comes from individual case series, about 13 published patients. There is no registry or EHR data.

2. Etiology

• Cause. The disease is monogenic: biallelic loss-of-function or hypomorphic variants in VPS41.
• Risk factors.
• Consanguinity: several families were consanguineous (Saudi, Iranian and Turkish families; Family 2 in van der Welle).
• Founder allele: p.Ser285Pro occurred in two unrelated Saudi families.
• Not reported: environmental risk factors, protective factors, modifier genes and gene-environment interactions.

3. Phenotypes

Frequencies use the 9 patients in Sanderson (Table 1, PMID:33764426), plus van der Welle (n=3), Steel (n=1) and Nakamura (n=1).

• Onset: infancy, from the neonatal period to the first year.
• Course: progressive.
• Severity: usually severe. Most patients cannot walk independently, and several use wheelchairs.
• Quality of life: no formal quality-of-life studies exist.
• Normal findings: nerve conduction was normal where tested.

4. Genetic and molecular information

• Gene: VPS41 (VPS41 subunit of HOPS complex), transcript NM_014396.
• HGNC ID: I believe it is HGNC:12713. This is unverified. The ID is not in cache/hgnc/terms.csv, and the OLS lookup was not permitted in this session. Confirm it with just validate-terms before binding.
• Reported variants:

• Variant origin: all germline.
• Mechanism: loss of function or hypomorphic alleles. Complete loss is probably lethal, since the Vps41 knockout mouse dies in early embryogenesis.

  "VPS41 knockout mice die early in utero, signifying VPS41 as an essential protein for embryonic development" (PMID:33851776)

• ClinGen / ClinVar: no ClinGen gene-disease validity curation was found, so leave gene_disease_validity absent. PanelApp Australia rates VPS41 green.
• Not reported: modifier genes, epigenetic contributions and chromosomal abnormalities.
• Incidental findings: van der Welle patient 1 also carried a 1q21.1 duplication, and patient 3 a homozygous UPF3A variant of uncertain significance.

5. Environmental information

Not applicable. No environmental, lifestyle or infectious factors have been reported.

6. Mechanism and pathophysiology

Ordered causal chain

1. Biallelic VPS41 variants (missense, nonsense or splice) reduce VPS41 protein abundance or function. This is shown directly: patient and rescue constructs had lower protein, and the Nakamura alleles reduced transcript and protein.
2. This prevents assembly of a functional HOPS tethering complex (demonstrated in patient fibroblasts and HeLa cells).

   "All mutants prevented formation of a functional HOPS complex, causing delayed lysosomal delivery of endocytic and autophagic cargo." (PMID:33851776)

3. Endolysosomal and autophagosome-lysosome fusion is impaired, which delays cargo delivery to lysosomes that are otherwise functional (demonstrated).

   "VPS41 patients represent a new class of lysosomal disorders in which lysosomes are functional, but insufficiently reached by cargo due to a trafficking defect." (PMID:33851776)

4. The pathway branches at this point (demonstrated in vitro):
5. 4a. mTORC1 cannot regulate TFEB/TFE3. mTORC1 redistributes to the cytosol, and TFE3/TFEB stay constitutively nuclear. This leads to continuous upregulation of lysosomal biogenesis (LAMP2 up) and autophagosome formation (LC3-II up). Autophagy responds less to starvation. Phosphorylation of S6K1 and 4EBP1 is preserved, so the defect is specific to the TFEB/TFE3 arm. > "the disease‐causing mutations specifically impair mTORC1 activity toward TFE3 and TFEB, causing constitutive activation of these transcription factors" (PMID:33851776)
6. 4b. Abnormal lysosome-related organelles accumulate: multilayered vesicles in lymphocytes, enlarged acidic compartments, and pigment defects in zebrafish melanosomes and retinal pigment epithelium.
7. 4c. VPS41's HOPS-independent role in regulated secretion is preserved for S285P. This is a negative result.
8. Lysosomal dysfunction in neural cells. In zebrafish vps41 crispants (mosaic F0 knockouts):
9. microglia are swollen and amoeboid with large acidic compartments, and LysoTracker signal rises across the whole brain;
10. wild-type mRNA rescues the brain LysoTracker signal.

The evidence here is from a model organism. 6. Purkinje cell and cerebellar dysfunction, then cerebellar atrophy. This step is inferred. Zebrafish showed a cerebellar-type optokinetic defect, but no visible Purkinje cell loss. VPS41 is highly expressed in Purkinje cells.

"A scenario of reduced viability of Purkinje cells is also plausible for VPS41-related ataxia" (PMID:33764426) 7. Clinical outcome: ataxia, dystonia, nystagmus, developmental delay and intellectual disability, with progressive vermian atrophy. Dystonia probably also involves basal ganglia circuits. This is inferred from the HOPSAND parallel; iron deposition was seen in 2 patients.

A second, protective role is also lost. VPS41 normally protects dopaminergic neurons against α-synuclein, and patient alleles lose this activity in C. elegans:

"co-expression of VPS41S285P /VPS41R662* abolished the neuroprotective function of VPS41 against α-synuclein aggregates" (PMID:33851776)

Suggested ontology terms

• GO biological processes:
• GO:1902774 late endosome to lysosome transport
• GO:0061909 autophagosome-lysosome fusion
• GO:0097352 autophagosome maturation
• GO:0007040 lysosome organization
• GO:0016236 macroautophagy
• GO:0008333 endosome to lysosome transport
• GO:0032008 positive regulation of TOR signaling (use with care; the defect is selective to TFEB/TFE3)
• GO cellular component: GO:0030897 HOPS complex
• CL cell types:
• CL:0000121 Purkinje cell
• CL:0000129 microglial cell
• CL:0000057 fibroblast (patient cells)
• CL:0000542 lymphocyte
• CL:0000148 melanocyte (zebrafish)
• CL:0000700 dopaminergic neuron (C. elegans)
• Molecular profiling: no transcriptomic, proteomic, metabolomic, single-cell or CRISPR-screen data exist for this disease. Sanderson did a co-expression analysis (105 genes) enriched for vesicle transport, phagosome maturation and autophagy terms.

7. Anatomical structures affected

• Primary: cerebellum (UBERON:0002037), especially the cerebellar vermis (UBERON:0004720).
• Also affected:
• corpus callosum (UBERON:0002336)
• basal ganglia (UBERON:0002420): iron deposition, caudate hyperintensity
• retina (UBERON:0000966): pigmentary changes
• brainstem and cerebral cortex atrophy in severe cases
• Musculoskeletal (secondary): contractures, thoracic deformity, kyphosis, swan-neck deformity, pes cavus.
• Subcellular: late endosome, lysosome and autophagosome compartments; the HOPS complex.
• Laterality: bilateral and symmetric.

8. Temporal development

• Onset: congenital or infantile (neonatal hypotonia; developmental delay in the first year).
• Course: chronic and progressive.
• Serial MRI showed vermis volume loss: normal vermis at 21 months, volume loss at 4 years 7 months.
• Two patients regressed.
• Lower-limb spasticity appeared from age 5 in one patient.
• Survival: patients reached at least 27–28 years of age.
• Not described: formal disease stages and remission.

9. Inheritance and population

• Inheritance: autosomal recessive (HP:0000007).
• Both homozygous variants (often in consanguineous families) and compound heterozygous variants occur.
• Parents and sibling carriers are unaffected.
• Not reported: penetrance (appears complete), anticipation, and mosaicism.
• Prevalence: unknown, ultra-rare. About 14 published patients:
• 9 in Sanderson
• 3 in van der Welle
• 1 in Steel
• 1 in Nakamura

Use measure_type: CASES_IN_LITERATURE. - Ancestries reported: Saudi Arab (founder p.Ser285Pro), Iranian, Brazilian, Turkish, Jewish (van der Welle family 2), European (van der Welle family 1, and Steel's patient) and Japanese. - Sex ratio: no bias evident (about 9 male, 4 female).

10. Diagnostics

• Genetic testing is the diagnostic test.
• Exome or genome sequencing, or an ataxia or dystonia gene panel. VPS41 is on PanelApp Australia panels.
• Long-read sequencing can establish phase when parental DNA is unavailable.
• RNA analysis can show splicing consequences.

  "Long‐read genome sequencing demonstrated that two VPS41 variants were in trans." (DOI:10.1002/mgg3.70285)

• Supportive tests:
• Brain MRI: vermian atrophy, thin corpus callosum, delayed myelination, basal ganglia iron.
• Electron microscopy of lymphocytes or fibroblasts: multilayered or vacuolar vesicles.
• Ophthalmologic examination.
• Standard lysosomal and metabolic screens (mucopolysaccharides, oligosaccharides, CDG) were normal, which helps the differential diagnosis.
• Differential diagnosis:
• other SCARs
• other HOPSANDs (VPS16, VPS11, VPS33A/mucopolysaccharidosis-plus)
• neurodegeneration with brain iron accumulation (NBIA)
• Hermansky-Pudlak syndrome
• congenital disorders of glycosylation (CDG)
• lysosomal storage disorders
• Clinical criteria and screening: there are no formal diagnostic criteria. Carrier testing and cascade testing apply to known families.

11. Outcome and prognosis

• Most patients have a severe, lifelong disability and cannot walk independently.
• No mortality data are available. Patients are reported alive into their late 20s.
• Complications include contractures, scoliosis or kyphosis, epilepsy (2 patients), recurrent infections and hearing loss (van der Welle patient 3).
• No prognostic biomarkers are known.

12. Treatment

• No disease-modifying therapy and no clinical trials were found.
• Supportive care, with suggested NCIT terms:
• Physical Therapy (NCIT:C15302)
• Occupational Therapy (NCIT:C121351)
• Speech-language therapy (NCIT:C159273)
• antiseizure Pharmacotherapy (NCIT:C15986)
• Supportive Care (NCIT:C15747)
• Genetic Counseling (NCIT:C15240)
• Proposed only, not tested: targeting the mTORC1–TFEB/TFE3 axis or lysosomal-autophagy pathways.

  "potential importance for treatment of HOPS‐related disorders" (PMID:33851776)

13. Prevention

There is no primary prevention. Options are: - genetic counseling (25% recurrence risk for carrier parents) - carrier testing of relatives - prenatal or preimplantation diagnosis once the familial variants are known

Tertiary prevention means managing orthopaedic complications and seizures.

14. Other species

No naturally occurring animal disease was found; OMIA was not checked. VPS41 is conserved: zebrafish vps41 shares 82% amino-acid identity with the human protein, and yeast Vps41 is the founding vacuolar-sorting gene.

15. Model organisms

Open items before curating the entry

• Confirm the VPS41 HGNC CURIE.
• The HP terms marked "(verify)" are not in cache/hp/terms.csv. Check each against HPO before binding it.
• PubMed PMIDs for Steel 2020, Monfrini 2021 and Nakamura 2026 were not retrieved. The DOI-keyed cache files can be cited as they are.
• No GeneReviews chapter is expected for this disease, but this was not confirmed. just check-genereviews will answer it offline.
• The five reference cache files fetched in this session have not been committed yet:
• PMID_33764426.md
• PMID_33851776.md
• DOI_10.1002_ana.25879.md
• DOI_10.1093_brain_awab161.md
• DOI_10.1002_mgg3.70285.md

Sources: Sanderson 2021, PMC8041041 · van der Welle 2021, PMC8103106 · Steel 2020, Ann Neurol · Monfrini 2021 (UCL Discovery) · Nakamura 2026, MGGM · NCBI MedGen 1788435 · MalaCards SCAR29 · PanelApp Australia VPS41

Reference Validation

Checked with linkml-reference-validator 0.3.0.

Quotes not found in the cited source

Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

Every one of these was searched against an abstract alone, with no full text retrieved - marked abstract only below. Where full text can be fetched, re-running with it will settle them; where the source publishes only a summary to PubMed, as GeneReviews chapters do, it will not, and the quote has to be checked by hand against the chapter itself.

• DOI:10.1002/ana.25879 (abstract only): "biallelic loss‐of‐function variants in VPS41 … in an individual with infantile‐onset generalized dystonia"
• closest text in source: "We also identified biallelic loss‐of‐function variants in VPS41 , another HOPS‐complex encoding gene, in an individual with infantile‐onset generalized dystonia"

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

• HP:0007772 (1 mention) - the report calls it "verify"; HP calls it Impaired smooth pursuit
• HP:0001250 (1 mention) - the report calls it "Seizures (therapy-resistant epilepsy)"; HP calls it Seizure
• HP:0002376 (1 mention) - the report calls it "verify"; HP calls it Developmental regression
• HP:0002058 (1 mention) - the report calls it "verify"; HP calls it Myopathic facies
• HP:0012675 (1 mention) - the report calls it "verify"; HP calls it Iron accumulation in brain

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

• HP:0002079 (1 mention) - the report calls it "Thin or hypoplastic corpus callosum (agenesis in one patient)"; HP calls it Hypoplasia of the corpus callosum, and lists "Hypoplastic corpus callosum" among its other names
• HP:0007703 (1 mention) - the report calls it "Retinal pigment abnormality or transient retinal dystrophy"; HP calls it Abnormal retinal pigmentation, and lists "Retinal pigmentary anomaly" among its other names
• HP:0001257 (1 mention) - the report calls it "Spasticity (lower limbs)"; HP calls it Spasticity
• HP:0001508 (1 mention) - the report calls it "Failure to thrive, contractures"; HP calls it Failure to thrive
• UBERON:0002037 (1 mention) - the report calls it "Primary: cerebellum"; UBERON calls it cerebellum**
• UBERON:0002420 (1 mention) - the report calls it "basal ganglia"; UBERON calls it basal ganglion, and lists "basal ganglia" among its other names
• NCIT:C15986 (1 mention) - the report calls it "antiseizure Pharmacotherapy"; NCIT calls it Pharmacotherapy