Is BLM p.Lys662fs (c.1985_1986del) pathogenic?

BLM p.Lys662fs (c.19851986del) is classified Pathogenic in BLM (ClinVar, Multiple submitters, 7 submitters; last evaluated 2025-08-04). Very rare (popmax 0.0011%, sas); Associated with Bloom syndrome.

What condition is associated with BLM p.Lys662fs (c.1985_1986del)?

BLM p.Lys662fs (c.1985_1986del) is associated with Bloom syndrome (ClinVar).

How common is BLM p.Lys662fs (c.1985_1986del) in the general population?

BLM p.Lys662fs (c.1985_1986del) is very rare (popmax 0.0011%, sas) (gnomAD).

How is Bloom syndrome inherited?

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

BLM p.Lys662fs

c.1985_1986del · rs762804291 · VCV553499

Pathogenic Multiple submitters

Classification

Pathogenic

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 7 submitters

Consequence

frameshift

predicted LoF

gnomAD v4.1

Rare

very rare (popmax 0.0011%, sas)

Conditions

Bloom syndrome

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Consequence	frameshift	predicted loss-of-function
NMD	predicted	premature termination codon in exon 8 of 22
Splicing
SpliceAI	—	not assessed · substitutions only
Constraint at this position
Conservation	phyloP 0.13	GERP -3.4, phastCons 0.98

Predicted loss-of-function is descriptive, not an applied PVS1 code.

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.0011% South Asian · 1/91,084 alleles

Overall 0.000137% 2/1,461,814 alleles · very rare

Ancestry group	Frequency	1 in
South Asiangrpmax	0.0011%	91,084
European (non-Finnish)	8.47e-05%	1,180,002

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.Lys662fs
Coding: c.1985_1986del
MANE Select: NM_000057
dbSNP: rs762804291
Type: Deletion
Location: chr15:90763064 (GRCh38)
Gene constraint: LOEUF 0.847 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 61.10 · 16 PDB

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.Lys662= Likely benign ★ same residue
BLM c.2193+1_2193+9del Pathogenic/Likely pathogenic ★★ same condition
BLM c.3013_3019+4del Likely pathogenic ★★ same condition
BLM c.3210+2del Pathogenic/Likely pathogenic ★★ same condition
BLM c.99-8_112del Pathogenic/Likely pathogenic ★★ same condition
BLM p.Arg545fs Pathogenic/Likely pathogenic ★★ same condition
BLM p.Arg836fs Pathogenic ★★ same condition
BLM p.Arg85fs Pathogenic/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-lys662fs (accessed [today's date]).

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