Classic homocystinuria: genes and variants
Explore variant evidence for Classic homocystinuria across 1 analyzed protein (CBS). Linked ClinVar records include 37 pathogenic or likely pathogenic variants, 51 variants of uncertain significance and 25 with conflicting classifications.
Coverage includes proteins already analyzed in CATVariant, not every gene involved in this condition. Database links are associations, not an assessment of clinical gene–disease validity. Computable evidence prioritizes variants for expert review and does not reclassify them. Counts refer to the selected disease label.
Data updated 2026-10-11. Automated aggregation, not a clinical review date.
Download variant evidence (CSV)
Genes linked to Classic homocystinuria
CBS: Cystathionine beta-synthase
A vitamin B6-dependent enzyme that combines homocysteine and serine to form cystathionine in the transsulfuration pathway. Deficiency causes homocystinuria.
37 ClinVar pathogenic / likely pathogenic and 76 uncertain variants in CBS have source records linked to Classic homocystinuria. Association strength is not clinical gene validity.
ClinVar pathogenic and likely pathogenic variants linked to Classic homocystinuria
| Variant | Position | Protein part | Clinical label |
|---|---|---|---|
| CBS R121L | 121 | Pathogenic / likely pathogenic (★★) | |
| CBS R121H | 121 | Pathogenic / likely pathogenic (★★) | |
| CBS N228K | 228 | Pathogenic / likely pathogenic (★★) | |
| CBS G151R | 151 | Pathogenic / likely pathogenic (★★) | |
| CBS G85R | 85 | Pathogenic / likely pathogenic (★★) | |
| CBS G116R | 116 | Pathogenic / likely pathogenic (★★) | |
| CBS P145L | 145 | Pathogenic / likely pathogenic (★★) | |
| CBS G148R | 148 | Pathogenic / likely pathogenic (★★) | |
| CBS C165Y | 165 | Pathogenic / likely pathogenic (★★) | |
| CBS N228S | 228 | Pathogenic / likely pathogenic (★★) | |
| CBS G259S | 259 | Pathogenic / likely pathogenic (★★) | |
| CBS G153R | 153 | Pathogenic / likely pathogenic (★★) | |
| CBS R336H | 336 | Pathogenic / likely pathogenic (★★) | |
| CBS E176K | 176 | Pathogenic / likely pathogenic (★★) | |
| CBS R379Q | 379 | Pathogenic / likely pathogenic (★★) | |
| CBS P88S | 88 | Pathogenic / likely pathogenic (★★) | |
| CBS L136P | 136 | Pathogenic / likely pathogenic (★★) | |
| CBS I143M | 143 | Pathogenic / likely pathogenic (★★) | |
| CBS L338P | 338 | Pathogenic / likely pathogenic (★★) | |
| CBS K384N | 384 | Pathogenic / likely pathogenic (★★) | |
| CBS L456P | 456 | CBS | Pathogenic / likely pathogenic (★★) |
| CBS A183T | 183 | Pathogenic / likely pathogenic (★★) | |
| CBS R317G | 317 | Pathogenic / likely pathogenic (★★) | |
| CBS G11R | 11 | Pathogenic / likely pathogenic (★★) | |
| CBS T262A | 262 | Pathogenic / likely pathogenic (★★) | |
| CBS I278S | 278 | Pathogenic / likely pathogenic (★★) | |
| CBS A288T | 288 | Pathogenic / likely pathogenic (★★) | |
| CBS G151V | 151 | Pathogenic / likely pathogenic (★) | |
| CBS G256V | 256 | Pathogenic / likely pathogenic (★) | |
| CBS R266G | 266 | Pathogenic / likely pathogenic (★) | |
| CBS L230Q | 230 | Pathogenic / likely pathogenic (★) | |
| CBS G305R | 305 | Pathogenic / likely pathogenic (★) | |
| CBS C346R | 346 | Pathogenic / likely pathogenic (★) | |
| CBS S349N | 349 | Pathogenic / likely pathogenic (★) | |
| CBS G453R | 453 | CBS | Pathogenic / likely pathogenic (★) |
| CBS L540Q | 540 | Pathogenic / likely pathogenic (★) | |
| CBS V314A | 314 | Pathogenic / likely pathogenic |
Uncertain variants prioritized for review in Classic homocystinuria
| Variant | Position | Protein part | Clinical label | Evidence |
|---|---|---|---|---|
| CBS S349R | 349 | Conflicting reports (★) | +6: 2 other pathogenic changes within 3 positions; S349N at the same position is pathogenic; not seen in the gnomAD population database; AlphaMissense 0.99 | |
| CBS P88A | 88 | Conflicting reports (★) | +6: 2 other pathogenic changes within 3 positions; P88S at the same position is pathogenic; not seen in the gnomAD population database; AlphaMissense 0.75 | |
| CBS G453W | 453 | CBS | Uncertain (★) | +6: 2 other pathogenic changes within 3 positions; G453R at the same position is pathogenic; not seen in the gnomAD population database; AlphaMissense 0.70 |
Same protein, different disease
- Hyperhomocysteinemia, thrombotic, cbs-related also has ClinVar records linked to CBS variants; they fall partly in the same places as the Classic homocystinuria variants (59 pathogenic / likely pathogenic).
- Homocystinuria also has ClinVar records linked to CBS variants; they fall partly in the same places as the Classic homocystinuria variants (51 pathogenic / likely pathogenic).
- Familial thoracic aortic aneurysm and aortic dissection also has ClinVar records linked to CBS variants; they fall in the same places as the Classic homocystinuria variants (8 pathogenic / likely pathogenic).
Diseases related to Classic homocystinuria
- Familial thoracic aortic aneurysm and aortic dissection, also linked to CBS
- Hyperhomocysteinemia, thrombotic, cbs-related, also linked to CBS
- Homocystinuria, also linked to CBS
- Connective tissue disease, also linked to CBS
- Thoracic aortic aneurysm or dissection, also linked to CBS
Frequently asked questions
Which genes have records linked to Classic homocystinuria?
This view contains 1 analyzed proteins: CBS. Links come from clinical records and association databases. They do not imply that every listed gene is a validated cause, and missing genes may not yet be analyzed.
What do the clinical classifications mean?
Linked records include 37 pathogenic or likely pathogenic variants, 51 variants of uncertain significance and 25 with conflicting classifications. Labels summarize source records; multi-condition records may not make a separate assertion for this disease. Check the original record and review status.
Does the evidence score change a VUS classification?
No. 3 VUS or conflicting variants reach the likely-pathogenic points range on the computable criteria available here. This is a research prioritization signal, not a clinical classification. Patient, family and other required evidence may be missing.
Can I download the variant evidence?
Download the CSV for all 140 variants in the selected disease scope, including clinical labels, review status, evidence criteria, predictor scores, functional measurements and population frequency where available.
About this data
Variant–disease links come from ClinVar, Open Targets and UniProt, pooled from eligible public CATVariant analyses of each human protein. Evidence scores use the ACMG/AMP Bayesian points scale with computable criteria only (position among known disease variants, rarity in gnomAD, calibrated predictors, deep mutational scanning); there is no family or patient data, so they prioritise variants for expert review and never classify them.
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