Is BLM p.Leu427Trp (c.1280T>G) pathogenic?

BLM p.Leu427Trp (c.1280T>G) is classified Uncertain significance in BLM (ClinVar, Multiple submitters, 2 submitters; last evaluated 2024-11-15). AlphaMissense: likely benign (0.1053); Very rare (popmax 0.000678%, nfe); Associated with hereditary neoplastic syndrome.

What condition is associated with BLM p.Leu427Trp (c.1280T>G)?

BLM p.Leu427Trp (c.1280T>G) is associated with hereditary neoplastic syndrome, Bloom syndrome (ClinVar).

How common is BLM p.Leu427Trp (c.1280T>G) in the general population?

BLM p.Leu427Trp (c.1280T>G) is very rare (popmax 0.000678%, nfe) (gnomAD).

What do computational predictors say about BLM p.Leu427Trp (c.1280T>G)?

AlphaMissense predicts likely benign (score 0.1053) — an in-silico prediction, not a clinical call.

BLM p.Leu427Trp

c.1280T>G · rs750960910 · VCV2143076

Uncertain significance Multiple submitters

Classification

Uncertain significance

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 2 submitters

AlphaMissense

likely benign

0.1053 · ACMG-weighted

gnomAD v4.1

Rare

very rare (popmax 0.000678%, nfe)

Missense predictors

0/3 damaging

AlphaMissense, REVEL, SaProt

Conditions

hereditary neoplastic syndrome

Computational evidence

Protein change
AlphaMissense	0.1053	likely benign
REVEL	0.099	moderately benign-leaning
SaProt	LLR -8.91	tolerated
⇒ AlphaMissense, REVEL and SaProt all call this tolerated.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP -0.92	GERP -5.3
Regional constraint	o/e 0.96	unconstrained · MANE · 16 kb · p 0.23 · regional, not allelic
Overall
CADD	3.836	PHRED · no single calibrated threshold — expert panels disagree

ClinVar classifies this uncertain; the computational predictors unanimously lean tolerated — a triage signal, not a reclassification

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

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.000678% European (non-Finnish) · 8/1,179,450 alleles

Filtering AF 0.000292% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000211%

Overall 0.000616% 9/1,461,076 alleles · very rare

Ancestry group	Frequency	1 in
Finnishnot grpmax-eligible	0.00156%	64,000
European (non-Finnish)grpmax	0.000678%	147,431

Finnish shows a higher raw frequency than the grpmax group above it. gnomAD excludes bottlenecked groups — Finnish, Ashkenazi Jewish, Amish and “Remaining individuals” — from grpmax, because founder effects make their frequencies unrepresentative for filtering. The table is sorted by frequency, so an excluded group can sit above the grpmax row.

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.Leu427Trp
Coding: c.1280T>G
MANE Select: NM_000057
dbSNP: rs750960910
Type: single nucleotide variant
Location: chr15:90760653 (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 427: the 'necessary for interaction with spidr' region

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.Leu427= Likely benign ★★ same residue
BLM p.Leu427Phe 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

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-leu427trp (accessed [today's date]).

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