Is SAMHD1 p.Arg56= (c.168C>T) pathogenic?

SAMHD1 p.Arg56= (c.168C>T) is classified Likely benign in SAMHD1 (ClinVar, Single submitter, 1 submitter; last evaluated 2024-02-27). Very rare (popmax 0.00102%, nfe); Associated with Aicardi-Goutieres syndrome 5.

What condition is associated with SAMHD1 p.Arg56= (c.168C>T)?

SAMHD1 p.Arg56= (c.168C>T) is associated with Aicardi-Goutieres syndrome 5 (ClinVar).

How common is SAMHD1 p.Arg56= (c.168C>T) in the general population?

SAMHD1 p.Arg56= (c.168C>T) is very rare (popmax 0.00102%, nfe) (gnomAD).

How is Aicardi-Goutières syndrome inherited?

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

SAMHD1 p.Arg56=

c.168C>T · rs370376351 · VCV1668677

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00102%, nfe)

Conditions

Aicardi-Goutieres syndrome 5

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Splicing
SpliceAI	<0.2	all four deltas below 0.2 · G>C here scores Δ0.27 · evaluated, not missing
Constraint at this position
Conservation	phyloP 0.5	GERP 0.61
Overall
CADD	8.65	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00102% European (non-Finnish) · 12/1,179,990 alleles

Filtering AF 0.000542% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000428%

Overall 0.000743% 12/1,614,140 alleles · very rare exomes 12/1,461,800 · genomes 0/152,340 · 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: SAMHD1
Protein: p.Arg56=
Coding: c.168C>T
MANE Select: NM_015474
dbSNP: rs370376351
Type: single nucleotide variant
Location: chr20:36951476 (GRCh38)
Gene constraint: LOEUF 0.889 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 88.45 · 76 PDB
Residue 56: the sam domain; an α-helix

Full SAMHD1 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

Aicardi-Goutieres syndrome 5 — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Aicardi-Goutières syndrome (Orphanet):

Inheritance: Autosomal dominant, Autosomal recessive
Onset: Antenatal, Infancy, Neonatal
Prevalence: 1-5 / 10 000 (Europe)

Similar variants

SAMHD1 p.Arg56His Uncertain significance ★★ ⚠ same residue
SAMHD1 c.1062+1G>T Pathogenic/Likely pathogenic ★★ same condition
SAMHD1 c.1411-2A>G Pathogenic ★★ same condition
SAMHD1 c.509+1G>A Likely pathogenic ★★ same condition
SAMHD1 c.626-1G>C Pathogenic/Likely pathogenic ★★ same condition
SAMHD1 p.Arg106Ter Pathogenic/Likely pathogenic ★★ same condition
SAMHD1 p.Arg134Ter Pathogenic/Likely pathogenic ★★ same condition
SAMHD1 p.Arg143Cys Pathogenic/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/samhd1-p-arg56 (accessed [today's date]).

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