Is FTCD p.Ala66Val (c.197C>T) pathogenic?

FTCD p.Ala66Val (c.197C>T) is classified Uncertain significance in FTCD (ClinVar, Multiple submitters, 2 submitters; last evaluated 2022-06-14). AlphaMissense: ambiguous (0.405); Very rare (popmax 0.00712%, nfe); Associated with formiminoglutamic aciduria.

What condition is associated with FTCD p.Ala66Val (c.197C>T)?

FTCD p.Ala66Val (c.197C>T) is associated with formiminoglutamic aciduria (ClinVar).

How common is FTCD p.Ala66Val (c.197C>T) in the general population?

FTCD p.Ala66Val (c.197C>T) is very rare (popmax 0.00712%, nfe) (gnomAD).

How is Formiminoglutamic aciduria inherited?

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

What do computational predictors say about FTCD p.Ala66Val (c.197C>T)?

AlphaMissense predicts ambiguous (score 0.405) — an in-silico prediction, not a clinical call.

FTCD p.Ala66Val

c.197C>T · rs199867833 · VCV502351

Uncertain significance Multiple submitters

Classification

Uncertain significance

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 2 submitters

AlphaMissense

ambiguous

0.405 · ACMG-weighted

gnomAD v4.1

Rare

very rare (popmax 0.00712%, nfe)

Conditions

formiminoglutamic aciduria

Computational evidence

Protein change
AlphaMissense	0.405	ambiguous
REVEL	0.463	indeterminate
SaProt	LLR -9.01	tolerated
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 11	GERP 1.4, phastCons 1
Regional constraint	o/e 1.12	unconstrained · MANE · 19 kb · p 0.00063 · regional, not allelic
Overall
CADD	24.4	PHRED · no single calibrated threshold — expert panels disagree

AlphaMissense carries the ACMG weight for missense; REVEL and SaProt are independent agreement signals.

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00712% European (non-Finnish) · 84/1,179,992 alleles

Filtering AF 0.00588% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00541%

Overall 0.00589% 95/1,612,728 alleles · very rare exomes 92/1,460,508 · genomes 3/152,220 · joint denominator

Ancestry group	Frequency	1 in
Remaining individualsnot grpmax-eligible	0.0144%	6,941
European (non-Finnish)grpmax	0.00712%	14,048
Admixed American	0.00333%	30,007

Remaining individuals shows a higher raw frequency than the grpmax group above it. gnomAD excludes bottlenecked groups — Finnish, Ashkenazi Jewish, Amish and “Remaining individuals” — from grpmax, because founder effects make their frequencies unrepresentative for filtering. The table is sorted by frequency, so an excluded group can sit above the grpmax row.

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.Ala66Val
Coding: c.197C>T
MANE Select: NM_206965
dbSNP: rs199867833
Type: single nucleotide variant
Location: chr21:46154190 (GRCh38)
Gene constraint: LOEUF 1.61 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 95.30
Residue 66: the 'formiminotransferase n-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.Ala66= Likely benign ★ same residue
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

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-ala66val (accessed [today's date]).

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