Is ADA p.Leu168= (c.504G>A) pathogenic?

ADA p.Leu168= (c.504G>A) is classified Likely benign in ADA (ClinVar, Single submitter, 1 submitter; last evaluated 2025-12-04). Very rare (popmax 0.00659%, 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.Leu168= (c.504G>A) in the general population?

ADA p.Leu168= (c.504G>A) is very rare (popmax 0.00659%, sas) (gnomAD).

ADA p.Leu168=

Q: What condition is associated with ADA p.Leu168= (c.504G>A)?

ADA p.Leu168= (c.504G>A) 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.504G>A · rs759425144 · VCV1571029

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00659%, sas)

Conditions

severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase 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 -0.17	GERP 1.5, phastCons 0.29
Overall
CADD	9.445	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00659% South Asian · 6/91,072 alleles

Filtering AF 0.00286% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00195%

Overall 0.000547% 8/1,461,592 alleles · very rare

Ancestry group	Frequency	1 in
South Asiangrpmax	0.00659%	15,179
European (non-Finnish)	0.00017%	589,964

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.Leu168=
Coding: c.504G>A
MANE Select: NM_000022
dbSNP: rs759425144
Type: single nucleotide variant
Location: chr20:44624304 (GRCh38)
Gene constraint: LOEUF 1.184 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 96.81 · 2 PDB
Residue 168: 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 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
ADA p.Arg149Trp 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/ada-p-leu168 (accessed [today's date]).

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