Is FTCD p.Cys313Ter (c.939C>A) pathogenic?

FTCD p.Cys313Ter (c.939C>A) is classified Likely pathogenic in FTCD (ClinVar, Single submitter, 1 submitter; last evaluated 2024-03-05). Very rare (popmax 8.5e-05%, nfe); Associated with formiminoglutamic aciduria.

What condition is associated with FTCD p.Cys313Ter (c.939C>A)?

FTCD p.Cys313Ter (c.939C>A) is associated with formiminoglutamic aciduria (ClinVar).

How common is FTCD p.Cys313Ter (c.939C>A) in the general population?

FTCD p.Cys313Ter (c.939C>A) is very rare (popmax 8.5e-05%, nfe) (gnomAD).

How is Formiminoglutamic aciduria inherited?

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

FTCD p.Cys313Ter

c.939C>A · VCV3587716

Likely pathogenic Single submitter

Classification

Likely pathogenic

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

Consequence

nonsense (stop-gain)

predicted LoF

gnomAD v4.1

Rare

very rare (popmax 8.5e-05%, nfe)

Conditions

formiminoglutamic aciduria

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Consequence	nonsense (stop-gain)	predicted loss-of-function
NMD	predicted	premature termination codon in exon 8 of 14
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP -1.3	GERP -3.6
Overall
CADD	34.0	PHRED · no single calibrated threshold — expert panels disagree

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

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 8.5e-05% European (non-Finnish) · 1/1,175,898 alleles

Overall 6.23e-05% 1/1,605,228 alleles · very rare exomes 1/1,452,932 · genomes 0/152,296 · joint denominator

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: FTCD
Protein: p.Cys313Ter
Coding: c.939C>A
MANE Select: NM_206965
Type: single nucleotide variant
Location: chr21:46146295 (GRCh38)
Gene constraint: LOEUF 1.61 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 95.30
Residue 313: the 'formiminotransferase c-subdomain' region

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

Disease context

formiminoglutamic aciduria — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Formiminoglutamic aciduria (Orphanet):

Inheritance: Autosomal recessive
Onset: Childhood

Similar variants

FTCD p.Arg255Ter Pathogenic ★★ same condition
FTCD p.Arg71Ter Pathogenic/Likely pathogenic ★★ same condition
FTCD p.Leu536Ter Pathogenic/Likely pathogenic ★★ same condition
FTCD p.Ala108Thr Uncertain significance ★★ ⚠ same condition
FTCD p.Ala159Val Uncertain significance ★★ ⚠ same condition
FTCD p.Ala368Val Uncertain significance ★★ ⚠ same condition
FTCD p.Ala418Thr Uncertain significance ★★ ⚠ same condition
FTCD p.Ala455Thr 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/ftcd-p-cys313ter (accessed [today's date]).

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