Is AGRN p.Cys877= (c.2631T>C) pathogenic?

AGRN p.Cys877= (c.2631T>C) is classified Likely benign in AGRN (ClinVar, Single submitter, 1 submitter; last evaluated 2023-11-19). Ultra-rare (popmax 0.0121%, nfe); Associated with congenital myasthenic syndrome 8.

What condition is associated with AGRN p.Cys877= (c.2631T>C)?

AGRN p.Cys877= (c.2631T>C) is associated with congenital myasthenic syndrome 8 (ClinVar).

How common is AGRN p.Cys877= (c.2631T>C) in the general population?

AGRN p.Cys877= (c.2631T>C) is ultra-rare (popmax 0.0121%, nfe) (gnomAD).

AGRN p.Cys877=

c.2631T>C · rs545849353 · VCV1133774

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

ultra-rare (popmax 0.0121%, nfe)

Conditions

congenital myasthenic syndrome 8

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 -4.4	GERP -3.3
Overall
CADD	2.266	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.0121% European (non-Finnish) · 143/1,179,892 alleles

Filtering AF 0.0105% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00981%

Overall 0.00924% 149/1,612,470 alleles · ultra-rare exomes 144/1,460,376 · genomes 5/152,094 · joint denominator

Ancestry group	Frequency	1 in
European (non-Finnish)grpmax	0.0121%	8,251
Remaining individualsnot grpmax-eligible	0.0048%	20,820
Finnishnot grpmax-eligible	0.00478%	20,901

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: AGRN
Protein: p.Cys877=
Coding: c.2631T>C
MANE Select: NM_198576
dbSNP: rs545849353
Type: single nucleotide variant
Location: chr1:1045827 (GRCh38)
Gene constraint: LOEUF 0.73 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 69.79 · 1 PDB
Residue 877: the laminin egf-like 2 domain; a disulfide bond

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

Disease context

congenital myasthenic syndrome 8 — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Similar variants

AGRN c.3632-1G>C Likely pathogenic ★★ same condition
AGRN p.Arg1671Ter Pathogenic/Likely pathogenic ★★ same condition
AGRN p.Arg834Ter Pathogenic/Likely pathogenic ★★ same condition
AGRN p.Gly1582Arg Pathogenic ★★ same condition
AGRN p.Gly1675Ser Pathogenic/Likely pathogenic ★★ same condition
AGRN c.1177+4A>G Uncertain significance ★★ same condition
AGRN c.1384+6C>T Uncertain significance ★★ same condition
AGRN c.4879+4G>A Uncertain significance ★★ 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/agrn-p-cys877 (accessed [today's date]).

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