Is CTPS1 p.Glu66= (c.198A>G) pathogenic?

CTPS1 p.Glu66= (c.198A>G) is classified Likely benign in CTPS1 (ClinVar, Single submitter, 1 submitter; last evaluated 2023-08-04). Very rare (popmax 0.000172%, nfe); Associated with combined immunodeficiency due to CTPS1 deficiency.

What condition is associated with CTPS1 p.Glu66= (c.198A>G)?

CTPS1 p.Glu66= (c.198A>G) is associated with combined immunodeficiency due to CTPS1 deficiency (ClinVar).

How common is CTPS1 p.Glu66= (c.198A>G) in the general population?

CTPS1 p.Glu66= (c.198A>G) is very rare (popmax 0.000172%, nfe) (gnomAD).

CTPS1 p.Glu66=

Q: How is Severe combined immunodeficiency due to CTPS1 deficiency inherited?

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

c.198A>G · rs1249411072 · VCV2809715

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.000172%, nfe)

Conditions

combined immunodeficiency due to CTPS1 deficiency

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 0.88	GERP -5.2, phastCons 0.98
Overall
CADD	7.655	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.000172% European (non-Finnish) · 2/1,163,626 alleles

Filtering AF 2.9e-05% ClinGen BA1/BS1 input FAF95, joint · FAF99 1.1e-05%

Overall 0.000139% 2/1,436,280 alleles · very rare

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: CTPS1
Protein: p.Glu66=
Coding: c.198A>G
MANE Select: NM_001905
dbSNP: rs1249411072
Type: single nucleotide variant
Location: chr1:40984852 (GRCh38)
Gene constraint: LOEUF 0.423 · pLI 1.00 (gnomAD)
Structure: AlphaFold pLDDT 91.46 · 7 PDB

Full CTPS1 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

combined immunodeficiency due to CTPS1 deficiency — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Severe combined immunodeficiency due to CTPS1 deficiency (Orphanet):

Inheritance: Autosomal recessive
Onset: Childhood, Infancy, Neonatal

Similar variants

CTPS1 c.1692-1G>C Pathogenic ★★ same condition
CTPS1 c.1095-5T>G Uncertain significance ★★ same condition
CTPS1 p.Ala471Thr Uncertain significance ★★ ⚠ same condition
CTPS1 p.Arg102Trp Uncertain significance ★★ ⚠ same condition
CTPS1 p.Arg294His Uncertain significance ★★ ⚠ same condition
CTPS1 p.Arg376Gln Uncertain significance ★★ ⚠ same condition
CTPS1 p.Arg550Gln Uncertain significance ★★ ⚠ same condition
CTPS1 p.Asn412Ser 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/ctps1-p-glu66 (accessed [today's date]).

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