Is ADA p.Glu203Asp (c.609G>T) pathogenic?

ADA p.Glu203Asp (c.609G>T) is classified Uncertain significance in ADA (ClinVar, No assertion criteria, 1 submitter; last evaluated 2025-03-10). AlphaMissense: likely benign (0.1725); Very rare (popmax 0.0011%, sas); Associated with severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency.

How common is ADA p.Glu203Asp (c.609G>T) in the general population?

ADA p.Glu203Asp (c.609G>T) is very rare (popmax 0.0011%, sas) (gnomAD).

What do computational predictors say about ADA p.Glu203Asp (c.609G>T)?

AlphaMissense predicts likely benign (score 0.1725) — an in-silico prediction, not a clinical call.

ADA p.Glu203Asp

Q: What condition is associated with ADA p.Glu203Asp (c.609G>T)?

ADA p.Glu203Asp (c.609G>T) is associated with severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency (ClinVar).

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

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

c.609G>T · VCV4066522

Uncertain significance No assertion criteria

Classification

Uncertain significance

ClinVar

Review

No assertion criteria ☆☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely benign

0.1725 · ACMG-weighted

gnomAD v4.1

Rare

very rare (popmax 0.0011%, sas)

Missense predictors

0/2 damaging

AlphaMissense, SaProt · REVEL no call

Conditions

severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency

Computational evidence

Protein change
AlphaMissense	0.1725	likely benign
REVEL	0.523	indeterminate
SaProt	LLR -5.18	tolerated
⇒ AlphaMissense and SaProt both call this tolerated; REVEL makes no call.
Splicing
SpliceAI	<0.2	all four deltas below 0.2 · C>T here scores Δ0.26 · evaluated, not missing
Constraint at this position
Conservation	phyloP 0.004	GERP -2.2, phastCons 0.77
Regional constraint	o/e 0.94	unconstrained · MANE · 32 kb · p 0.21 · regional, not allelic
Overall
CADD	21.5	PHRED · no single calibrated threshold — expert panels disagree

ClinVar classifies this uncertain; the computational predictors unanimously lean tolerated — a triage signal, not a reclassification

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

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.0011% South Asian · 1/91,078 alleles

Overall 6.84e-05% 1/1,461,762 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: ADA
Protein: p.Glu203Asp
Coding: c.609G>T
MANE Select: NM_000022
Type: single nucleotide variant
Location: chr20:44623076 (GRCh38)
Gene constraint: LOEUF 1.184 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 96.81 · 2 PDB
Residue 203: an α-helix

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

Disease context

severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Severe combined immunodeficiency due to adenosine deaminase deficiency (Orphanet):

Inheritance: Autosomal recessive
Onset: Infancy, Neonatal
Prevalence: 1-9 / 1 000 000 (Europe)

Similar variants

ADA p.Glu203Ala Uncertain significance ★★★ ⚠ same residue
ADA c.1078+2T>A Likely pathogenic ★★★ same condition
ADA c.219-2A>G Likely pathogenic ★★★ same condition
ADA c.363-2A>G Likely pathogenic ★★★ same condition
ADA c.606+1G>T Likely pathogenic ★★★ same condition
ADA c.975+1G>A Pathogenic ★★★ same condition
ADA c.976-1G>C Pathogenic ★★★ same condition
ADA p.Ala329Val 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/ada-p-glu203asp (accessed [today's date]).

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