Variant
BTD C166Y
NM_001370658.1(BTD):c.497G>A (p.Cys166Tyr)
- p.Cys166Tyr
- p.C166Y
- rs397514369
- ClinVar classification
- Pathogenic/likely pathogenic
- Review status
- 2 stars out of 4criteria provided, multiple submitters, no conflicts
- Last evaluated
- 23 December 2025
Data current to ClinVar release 2026-10-19 · Dante Labs data release 2026.10.21-311f020eFacts last changed 21 October 2026
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C166Y is a missense variant in BTD: it changes a single amino acid in the protein the gene encodes. ClinVar classifies it as pathogenic or likely pathogenic for biotinidase deficiency (criteria provided, multiple submitters, no conflicts).
ClinVar classifications
| Condition | Classification | Review status | Submissions | Last evaluated |
|---|---|---|---|---|
| biotinidase deficiencyClinVar VCV000025020 (opens in a new tab) | Pathogenic/likely pathogenic | 2 stars out of 4criteria provided, multiple submitters, no conflicts | 8 submissions | 23 December 2025 |
Classifications as ClinVar records them in release 2026-10-19. ClinVar updates them as evidence is reviewed.
ACMG/AMP criteria
The ACMG/AMP criteria C166Y meets, from its predicted effect in BTD, gnomAD and ClinVar.
| Criterion | Strength | Points | Rests on |
|---|---|---|---|
| PM5A different pathogenic change at the same amino acid | Moderate | +2 | p.Cys166Gly at the same amino acid, ClinVar: Likely pathogenic (criteria provided, multiple submitters, no conflicts) |
| PM2Absent or very rare in population databases | Supporting | +1 | 0.0071% in gnomAD exomes |
| PP5A reputable source reports it as pathogenic | Supporting | Not counted | ClinVar: Pathogenic/likely pathogenic (criteria provided, multiple submitters, no conflicts) |
On these criteria alone: +3 points, uncertain significance.
Assessed automatically, without functional, computational or family evidence. Not a clinical classification.
Population frequency
How often C166Y is seen among the people whose exomes and genomes gnomAD 4.1 brings together.
| Dataset | Allele frequency | Allele count | Homozygotes | Commonest in |
|---|---|---|---|---|
| gnomAD exomes | 0.001%1 in 97,459 | 15 of 1,461,890 | 1 | Middle Eastern: 0.017% |
| gnomAD genomes | Not seen | 0 of 0 | 0 |
Figures from gnomAD 4.1, as gnomAD publishes them. Groups are genetic ancestry groups as gnomAD infers them. They describe the variant in gnomAD's populations, not anyone's result.
Molecular details
| Gene | BTD |
|---|---|
| Transcript | NM_001370658.1MANE Select |
| Coding DNA change (HGVS c.) | c.497G>A |
| Protein change (HGVS p.) | p.Cys166Tyrp.C166Y |
| Predicted consequence | Missensemissense_variant (opens in a new tab) |
| Predicted impact | Moderate |
| Position (GRCh38) | chr3:15644413 G>A |
| Position (GRCh37) | chr3:15685920 G>A |
| dbSNP ID | rs397514369 (opens in a new tab) |
| ClinVar Variation ID | VCV000025020 (opens in a new tab) |
| ClinVar Allele ID | 36357 |
| ClinGen Allele Registry ID | CA220327 (opens in a new tab) |
| ClinVar name | NM_001370658.1(BTD):c.497G>A (p.Cys166Tyr) |
BTD C166Y in other databases
Reports that look at this variant (2)
These Genome Test condition reports include C166Y among the variants they look at.
| Report | Conditions | Inheritance |
|---|---|---|
| Biotinidase & Holocarboxylase Deficiency | Biotinidase and Holocarboxylase Synthetase Deficiency (Multiple Carboxylase Deficiency) | Autosomal recessive |
| Rare Hereditary Peripheral Neuropathies | Hereditary Peripheral Neuropathy |
Other variants in BTD
- A142VPathogenic/likely pathogenic2 stars out of 4
- A217TPathogenic/likely pathogenic2 stars out of 4
- A269VPathogenic/likely pathogenic2 stars out of 4
- A279PPathogenic/likely pathogenic2 stars out of 4
- A419DPathogenic2 stars out of 4
- A458PPathogenic/likely pathogenic2 stars out of 4
- c.-17+1G>APathogenic/likely pathogenic2 stars out of 4
- c.-17+2T>CPathogenic/likely pathogenic2 stars out of 4
- c.250-15delPathogenic/likely pathogenic2 stars out of 4
- c.359G>APathogenic2 stars out of 4
Limitations
This page describes publicly available information about a genetic variant. It is not a diagnosis, and it says nothing about whether you or anyone else carries this variant.
Classifications come from ClinVar and change as new evidence is reviewed. A classification here may differ from the one in ClinVar today, or from the one a laboratory reports.
Whole genome sequencing with short reads can miss or miscall some variants, particularly in repeated or highly similar stretches of DNA and in large insertions, deletions or rearrangements.
If you have questions about a variant in your own results or in your family, talk to a genetic counsellor or your doctor.
Sources & credits
- Classifications from ClinVar (release 2026-10-19), National Center for Biotechnology Information.
- Condition terms from the Mondo Disease Ontology (release 2026-10-06), used under CC BY 4.0.
- Gene symbols and names from the HUGO Gene Nomenclature Committee (release 2026-10-16).
- Allele identifiers from the ClinGen Allele Registry (release 2026-10-21-c4908f54).
- Reference SNP identifiers from dbSNP (release b157), National Center for Biotechnology Information.
- Gene–disease links from the Gene Curation Coalition, GenCC (release 2026-10-21).
- Difficult regions from the Genome in a Bottle Consortium (release v3.6).
- Transcripts from MANE (release v1.5), NCBI and EMBL-EBI.
- Predicted consequences from mehari (release 0.11.0), with transcript models from cdot.
- Built from Dante Labs data release 2026.10.21-311f020e of 21 October 2026.
Cite this page
Dante Labs. (21 October 2026). BTD C166Y (c.497G>A, rs397514369) (Version 2026.10.21-311f020e). Retrieved 21 October 2026, from https://dantelabs.com/genes/btd/variants/c166y
Dante Labs. BTD C166Y (c.497G>A, rs397514369) [Internet]. Version 2026.10.21-311f020e. 21 October 2026 [cited 21 October 2026]. Available from: https://dantelabs.com/genes/btd/variants/c166y
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