Is BLM p.Leu1260Val (c.3778T>G) pathogenic?

BLM p.Leu1260Val (c.3778T>G) is classified Uncertain significance in BLM (ClinVar, Multiple submitters, 2 submitters; last evaluated 2021-09-23). AlphaMissense: ambiguous (0.4211); Absent from gnomAD v4.1; Associated with hereditary neoplastic syndrome.

What condition is associated with BLM p.Leu1260Val (c.3778T>G)?

BLM p.Leu1260Val (c.3778T>G) is associated with hereditary neoplastic syndrome, Bloom syndrome (ClinVar).

How common is BLM p.Leu1260Val (c.3778T>G) in the general population?

BLM p.Leu1260Val (c.3778T>G) is absent from gnomAD v4.1 (gnomAD).

What do computational predictors say about BLM p.Leu1260Val (c.3778T>G)?

AlphaMissense predicts ambiguous (score 0.4211) — an in-silico prediction, not a clinical call.

BLM p.Leu1260Val

c.3778T>G · rs2151198289 · VCV1499976

Uncertain significance Multiple submitters

Classification

Uncertain significance

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 2 submitters

AlphaMissense

ambiguous

0.4211 · ACMG-weighted

gnomAD v4.1

Absent

absent from gnomAD v4.1

Conditions

hereditary neoplastic syndrome

Computational evidence

Protein change
AlphaMissense	0.4211	ambiguous
REVEL	0.392	indeterminate
SaProt	LLR -10.22	damaging
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 5	GERP 1.6, phastCons 1
Regional constraint	o/e 0.92	unconstrained · MANE · 46 kb · p 0.035 · regional, not allelic
Overall
CADD	23.6	PHRED · no single calibrated threshold — expert panels disagree

AlphaMissense carries the ACMG weight for missense; REVEL and SaProt are independent agreement signals.

Population frequency

gnomAD v4.1 · exomes + genomes

Absent from gnomAD v4.1. Not observed in any sequenced alleles — a rarity signal (ACMG PM2-supporting), not evidence of pathogenicity on its own.

Variant & gene context

Gene: BLM
Protein: p.Leu1260Val
Coding: c.3778T>G
MANE Select: NM_000057
dbSNP: rs2151198289
Type: single nucleotide variant
Location: chr15:90809163 (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 1260: an α-helix; the hrdc domain

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.Leu1260Ter Pathogenic ★ same residue
BLM p.Leu1260= Likely benign ★ same residue
BLM p.Leu1260Phe 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

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-leu1260val (accessed [today's date]).

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