Bloom syndrome: genes and variants
Bloom syndrome is linked to 1 analyzed protein (BLM). 9 DNA variants are known to cause it; 1,736 more are uncertain, and 1 of those already look disease-causing on computable evidence.
Last updated 2026-09-30. Research information, not medical advice.
Genes linked to Bloom syndrome
BLM: RecQ-like DNA helicase BLM
It unwinds complex DNA structures and helps resolve homologous-recombination intermediates, thereby suppressing inappropriate sister-chromatid exchanges and maintaining genome stability. Biallelic loss-of-function variants cause Bloom syndrome, characterized by growth deficiency, chromosome instability, and marked cancer predisposition.
9 disease-causing and 1,736 uncertain variants in BLM are linked to Bloom syndrome.
Known disease-causing variants in Bloom syndrome
| Variant | Position | Protein part | Clinical label |
|---|---|---|---|
| BLM Q672R | 672 | Disease-causing (★★) | |
| BLM C1055S | 1055 | Disease-causing (★★) | |
| BLM C1055R | 1055 | Disease-causing (★★) | |
| BLM C901Y | 901 | Helicase C-terminal | Disease-causing (★★) |
| BLM D1064V | 1064 | Disease-causing (★★) | |
| BLM M814K | 814 | Helicase ATP-binding | Disease-causing |
| BLM M1L | 1 | Disease-causing | |
| BLM G952A | 952 | Helicase C-terminal | Disease-causing |
| BLM C1036F | 1036 | Disease-causing |
Uncertain variants in Bloom syndrome that look disease-causing
| Variant | Position | Protein part | Clinical label | Evidence |
|---|---|---|---|---|
| BLM C1055Y | 1055 | Conflicting reports (★) | +7: 2 other pathogenic changes within 3 positions; C1055S at the same position is pathogenic; seen in 1.4e-06 of gnomAD DNA copies; REVEL 0.851 |
Diseases related to Bloom syndrome
- Ovarian cancer, also linked to BLM
- Colorectal cancer, also linked to BLM
- Hereditary breast ovarian cancer syndrome, also linked to BLM
Frequently asked questions
Which genes are linked to Bloom syndrome?
In CATVariant, Bloom syndrome is linked to 1 analyzed protein: BLM (RecQ-like DNA helicase BLM).
How many genetic variants are linked to Bloom syndrome?
1,813 variants: 9 are classified as disease-causing (pathogenic or likely pathogenic) in ClinVar and 1,736 are of uncertain significance or have conflicting reports.
Which uncertain variants in Bloom syndrome look disease-causing?
1 uncertain variants reach the likely-pathogenic range of the ACMG/AMP points scale on computable evidence, for example BLM C1055Y. These are leads for expert review, not diagnoses.
About this data
Variant–disease links come from ClinVar, Open Targets and UniProt, pooled from the latest public CATVariant analysis 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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