Is GMPPB p.Val318= (c.954A>G) pathogenic?

GMPPB p.Val318= (c.954A>G) is classified Likely benign in GMPPB (ClinVar, Single submitter, 1 submitter; last evaluated 2025-09-13). Ultra-rare (popmax 0.02%, amr); Associated with muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A14.

What condition is associated with GMPPB p.Val318= (c.954A>G)?

GMPPB p.Val318= (c.954A>G) is associated with muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A14, muscular dystrophy-dystroglycanopathy (congenital with intellectual disability), type B14, autosomal recessive limb-girdle muscular dystrophy type 2T (ClinVar).

How common is GMPPB p.Val318= (c.954A>G) in the general population?

GMPPB p.Val318= (c.954A>G) is ultra-rare (popmax 0.02%, amr) (gnomAD).

How is Walker-Warburg syndrome inherited?

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

GMPPB p.Val318=

c.954A>G · rs747818187 · VCV1155602

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

ultra-rare (popmax 0.02%, amr)

Conditions

muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A14

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 -1.4	GERP -4.5
Overall
CADD	5.285	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.02% Admixed American · 12/60,004 alleles

Filtering AF 0.0115% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00898%

Overall 0.000991% 16/1,613,850 alleles · ultra-rare

Ancestry group	Frequency	1 in
Admixed Americangrpmax	0.02%	5,000
Remaining individualsnot grpmax-eligible	0.0064%	15,621

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: GMPPB
Protein: p.Val318=
Coding: c.954A>G
MANE Select: NM_021971
dbSNP: rs747818187
Type: single nucleotide variant
Location: chr3:49721881 (GRCh38)
Gene constraint: LOEUF 1.189 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 96.33 · 3 PDB
Residue 318: the 'hexapeptide repeat domain' region; a UniProt-annotated variant site (in mddgc14)

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

Disease context

muscular dystrophy-dystroglycanopathy (congenital with brain and eye anomalies), type A14 — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Also linked: muscular dystrophy-dystroglycanopathy (congenital with intellectual disability), type B14 autosomal recessive limb-girdle muscular dystrophy type 2T

For Walker-Warburg syndrome (Orphanet):

Inheritance: Autosomal recessive
Onset: Antenatal, Infancy, Neonatal
Prevalence: <1 / 1 000 000 (United Kingdom)

Similar variants

GMPPB p.Val318Ala Conflicting classifications of pathogenicity ★ same residue
GMPPB c.129+1G>T Likely pathogenic ★★ same condition
GMPPB c.402+1G>A Pathogenic/Likely pathogenic ★★ same condition
GMPPB c.640+1G>A Pathogenic/Likely pathogenic ★★ same condition
GMPPB c.640+1G>C Likely pathogenic ★★ same condition
GMPPB p.Arg185Cys Pathogenic/Likely pathogenic ★★ same condition
GMPPB p.Arg287Gln Pathogenic/Likely pathogenic ★★ ⚠ same condition
GMPPB p.Arg287Trp 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/gmppb-p-val318 (accessed [today's date]).

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