Is FKRP p.Cys6= (c.18C>T) pathogenic?

FKRP p.Cys6= (c.18C>T) is classified Likely benign in FKRP (ClinVar, Multiple submitters, 2 submitters; last evaluated 2026-01-08). Very rare (popmax 0.00534%, afr); Associated with muscular dystrophy-dystroglycanopathy, type A.

What condition is associated with FKRP p.Cys6= (c.18C>T)?

FKRP p.Cys6= (c.18C>T) is associated with muscular dystrophy-dystroglycanopathy, type A (ClinVar).

How common is FKRP p.Cys6= (c.18C>T) in the general population?

FKRP p.Cys6= (c.18C>T) is very rare (popmax 0.00534%, afr) (gnomAD).

How is Walker-Warburg syndrome inherited?

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

FKRP p.Cys6=

c.18C>T · rs373388363 · VCV698773

Likely benign Multiple submitters

Classification

Likely benign

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 2 submitters

gnomAD v4.1

Rare

very rare (popmax 0.00534%, afr)

Conditions

muscular dystrophy-dystroglycanopathy, type A

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 2.2	GERP -0.75, phastCons 1
Overall
CADD	12.17	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00534% African / African-American · 4/74,884 alleles

Filtering AF 0.00175% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00104%

Overall 0.000311% 5/1,607,918 alleles · very rare

Ancestry group	Frequency	1 in
African / African-Americangrpmax	0.00534%	18,721
Remaining individualsnot grpmax-eligible	0.00161%	62,292

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: FKRP
Protein: p.Cys6=
Coding: c.18C>T
MANE Select: NM_024301
dbSNP: rs373388363
Type: single nucleotide variant
Location: chr19:46755468 (GRCh38)
Gene constraint: LOEUF 1.543 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 94.08 · 8 PDB
Residue 6: a disulfide bond

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

Disease context

muscular dystrophy-dystroglycanopathy, type A — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Walker-Warburg syndrome (Orphanet):

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

Similar variants

FKRP p.Cys6Arg Uncertain significance ★★ ⚠ same residue
FKRP p.Ala157Pro Pathogenic/Likely pathogenic ★★ same condition
FKRP p.Ala321Glu Pathogenic/Likely pathogenic ★★ ⚠ same condition
FKRP p.Ala455Asp Pathogenic ★★ same condition
FKRP p.Arg176Ter Pathogenic/Likely pathogenic ★★ same condition
FKRP p.Arg275Cys Pathogenic/Likely pathogenic ★★ same condition
FKRP p.Arg54Gly Likely pathogenic ★★ ⚠ same condition
FKRP p.Asn463Asp 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/fkrp-p-cys6 (accessed [today's date]).

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