Is BLM p.Leu688Pro (c.2063T>C) pathogenic?

BLM p.Leu688Pro (c.2063T>C) is classified Uncertain significance in BLM (ClinVar, Single submitter, 1 submitter; last evaluated 2023-03-07). AlphaMissense: likely pathogenic (0.9977); Absent from gnomAD v4.1; Associated with Bloom syndrome.

What condition is associated with BLM p.Leu688Pro (c.2063T>C)?

BLM p.Leu688Pro (c.2063T>C) is associated with Bloom syndrome (ClinVar).

How common is BLM p.Leu688Pro (c.2063T>C) in the general population?

BLM p.Leu688Pro (c.2063T>C) is absent from gnomAD v4.1 (gnomAD).

How is Bloom syndrome inherited?

Typically Autosomal recessive (Orphanet). A genetic counselor can assess individual risk for a family.

What do computational predictors say about BLM p.Leu688Pro (c.2063T>C)?

AlphaMissense predicts likely pathogenic (score 0.9977) — an in-silico prediction, not a clinical call.

BLM p.Leu688Pro

c.2063T>C · rs2505435382 · VCV2185717

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely pathogenic

0.9977 · ACMG-weighted

gnomAD v4.1

Absent

absent from gnomAD v4.1

Missense predictors

3/3 damaging

AlphaMissense, REVEL, SaProt

Conditions

Bloom syndrome

Computational evidence

Protein change
AlphaMissense	0.9977	likely pathogenic · top 2% in BLM
REVEL	0.895	moderately pathogenic-leaning
SaProt	LLR -16.45	damaging
⇒ AlphaMissense, REVEL and SaProt all call this damaging.
Splicing
SpliceAI	<0.2	no splice effect predicted · four deltas, not one · how we know
Constraint at this position
Conservation	phyloP 7.8	GERP 2.6, phastCons 1
Regional constraint	o/e 0.36	unconstrained · MANE · 90 bp · p 0.00014 · regional, not allelic
Overall
CADD	29.1	PHRED · no single calibrated threshold — expert panels disagree

ClinVar classifies this uncertain; the computational predictors unanimously lean damaging — 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

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.Leu688Pro
Coding: c.2063T>C
MANE Select: NM_000057
dbSNP: rs2505435382
Type: single nucleotide variant
Location: chr15:90763146 (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 688: the helicase atp-binding domain; a β-strand

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

Disease context

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

For Bloom syndrome (Orphanet):

Inheritance: Autosomal recessive
Onset: Antenatal, Neonatal
Prevalence: 1-9 / 100 000 (Specific population)

Similar variants

BLM p.Leu688= Likely benign ★★ 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-leu688pro (accessed [today's date]).

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