Is BLM p.Cys799= (c.2397T>C) pathogenic?

BLM p.Cys799= (c.2397T>C) is classified Likely benign in BLM (ClinVar, Multiple submitters, 2 submitters; last evaluated 2026-01-31). Very rare (popmax 0.00255%, nfe); Associated with hereditary neoplastic syndrome.

What condition is associated with BLM p.Cys799= (c.2397T>C)?

BLM p.Cys799= (c.2397T>C) is associated with hereditary neoplastic syndrome, Bloom syndrome (ClinVar).

How common is BLM p.Cys799= (c.2397T>C) in the general population?

BLM p.Cys799= (c.2397T>C) is very rare (popmax 0.00255%, nfe) (gnomAD).

BLM p.Cys799=

c.2397T>C · rs771209978 · VCV454102

Likely benign Multiple submitters

Classification

Likely benign

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 2 submitters

gnomAD v4.1

Rare

very rare (popmax 0.00255%, nfe)

Conditions

hereditary neoplastic syndrome

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 1.5	GERP 1.6, phastCons 1
Overall
CADD	10.33	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00255% European (non-Finnish) · 30/1,175,680 alleles

Filtering AF 0.00181% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00157%

Overall 0.00193% 31/1,609,420 alleles · very rare exomes 31/1,457,072 · genomes 0/152,348 · joint denominator

Ancestry group	Frequency	1 in
European (non-Finnish)grpmax	0.00255%	39,189
Remaining individualsnot grpmax-eligible	0.0016%	62,346

Rarity supports pathogenicity (ACMG PM2); frequency above a disease-specific BA1/BS1 threshold argues against it. A variant frequent in one ancestry group can be near-absent in others, so a single global figure can mislead.

Variant & gene context

Gene: BLM
Protein: p.Cys799=
Coding: c.2397T>C
MANE Select: NM_000057
dbSNP: rs771209978
Type: single nucleotide variant
Location: chr15:90769222 (GRCh38)
Gene constraint: LOEUF 0.847 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 61.10 · 16 PDB
Residue 799: the helicase atp-binding domain; an α-helix

Full BLM gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

hereditary neoplastic syndrome — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Also linked: Bloom syndrome

Similar variants

BLM p.Cys799Phe Uncertain significance ★ ⚠ same residue
BLM c.1087+1G>A Likely pathogenic ★★ same condition
BLM c.1088-1G>A Likely pathogenic ★★ same condition
BLM c.1220+2T>C Likely pathogenic ★★ same condition
BLM c.1220+2T>G Likely pathogenic ★★ same condition
BLM c.1882+2T>C Likely pathogenic ★★ same condition
BLM c.2074+1G>T Likely pathogenic ★★ same condition
BLM c.2075-1G>A Likely pathogenic ★★ same condition

Built on 18 open, versioned datasets — ClinVar, gnomAD, AlphaMissense, REVEL, ClinGen & more — plus Sugi Variant's own cross-source analysis. Source data 2026-01–2026-10, ClinVar 2026-10. Full sources & versions →

Cite Sugi Variant

Gür T. Sugi Variant: A Deterministic Per-Variant Germline Reference from a Knowledge Graph for Humans and AI Agents. 2026. doi:10.5281/zenodo.21509445. This variant: https://sugi.bio/variant/blm-p-cys799 (accessed [today's date]).

Preprint & method: sugi.bio/variant/method Machine-readable: this page as Markdown