Is HTT p.Arg1268His (c.3803G>A) pathogenic?

HTT p.Arg1268His (c.3803G>A) is classified Uncertain significance in HTT (ClinVar, Single submitter, 1 submitter; last evaluated 2021-02-03). AlphaMissense: likely benign (0.0744); Very rare (popmax 0.00237%, sas).

How common is HTT p.Arg1268His (c.3803G>A) in the general population?

HTT p.Arg1268His (c.3803G>A) is very rare (popmax 0.00237%, sas) (gnomAD).

What do computational predictors say about HTT p.Arg1268His (c.3803G>A)?

AlphaMissense predicts likely benign (score 0.0744) — an in-silico prediction, not a clinical call.

HTT p.Arg1268His

c.3803G>A · rs199529839 · VCV1407461

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely benign

0.0744 · ACMG-weighted

gnomAD v4.1

Rare

very rare (popmax 0.00237%, sas)

Computational evidence

Protein change
AlphaMissense	0.0744	likely benign
REVEL	0.319	indeterminate
SaProt	—	not scored · why
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 12	GERP 1.5, phastCons 1
Overall
CADD	26.2	PHRED · no single calibrated threshold — expert panels disagree

AlphaMissense carries the ACMG weight for missense; REVEL is an independent agreement signal.

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00237% South Asian · 2/84,244 alleles

Filtering AF 0.000394% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000148%

Overall 0.000579% 9/1,554,708 alleles · very rare exomes 7/1,402,378 · genomes 2/152,330 · joint denominator

Ancestry group	Frequency	1 in
South Asiangrpmax	0.00237%	42,122
Remaining individualsnot grpmax-eligible	0.00166%	60,220
African / African-American	0.00136%	73,580
European (non-Finnish)	0.000436%	229,613

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: HTT
Protein: p.Arg1268His
Coding: c.3803G>A
MANE Select: NM_001388492
dbSNP: rs199529839
Type: single nucleotide variant
Location: chr4:3160331 (GRCh38)
Structure: AlphaFold pLDDT 85.38 · 30 PDB

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

Similar variants

HTT p.Arg1268Cys Uncertain significance ★ same residue
HTT c.889+6G>T Uncertain significance ★★ same type
HTT p.Ala2739Thr Uncertain significance ★★ same type
HTT p.Arg1654Trp Uncertain significance ★★ same type
HTT p.Arg1945Trp Uncertain significance ★★ same type
HTT p.Asp1157Gly Uncertain significance ★★ same type
HTT p.Asp920Asn Uncertain significance ★★ same type
HTT p.Glu449Ala Uncertain significance ★★ ⚠ same type

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/htt-p-arg1268his (accessed [today's date]).

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