Is HTT p.Arg1823Cys (c.5467C>T) pathogenic?

HTT p.Arg1823Cys (c.5467C>T) is classified Uncertain significance in HTT (ClinVar, Single submitter, 1 submitter; last evaluated 2021-02-03). AlphaMissense: likely benign (0.1115); Ultra-rare (popmax 0.0267%, eas).

How common is HTT p.Arg1823Cys (c.5467C>T) in the general population?

HTT p.Arg1823Cys (c.5467C>T) is ultra-rare (popmax 0.0267%, eas) (gnomAD).

What do computational predictors say about HTT p.Arg1823Cys (c.5467C>T)?

AlphaMissense predicts likely benign (score 0.1115) — an in-silico prediction, not a clinical call.

HTT p.Arg1823Cys

c.5467C>T · rs779984163 · VCV1403231

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely benign

0.1115 · ACMG-weighted

gnomAD v4.1

Rare

ultra-rare (popmax 0.0267%, eas)

Missense predictors

0/2 damaging

AlphaMissense, REVEL · SaProt no call

Computational evidence

Protein change
AlphaMissense	0.1115	likely benign
REVEL	0.137	moderately benign-leaning
SaProt	—	not scored · why
⇒ AlphaMissense and REVEL both call this tolerated; SaProt makes no call.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 4.7	GERP 2.4, phastCons 1
Overall
CADD	24.5	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 is an independent agreement signal.

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.0267% East Asian · 12/44,892 alleles

Filtering AF 0.0154% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.0121%

Overall 0.00118% 19/1,614,064 alleles · ultra-rare exomes 15/1,461,876 · genomes 4/152,188 · joint denominator

Ancestry group	Frequency	1 in
East Asiangrpmax	0.0267%	3,741
South Asian	0.00329%	30,361
Remaining individualsnot grpmax-eligible	0.0016%	62,490
European (non-Finnish)	0.000254%	393,345

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.Arg1823Cys
Coding: c.5467C>T
MANE Select: NM_001388492
dbSNP: rs779984163
Type: single nucleotide variant
Location: chr4:3199830 (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 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
HTT p.Gly2084Arg 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-arg1823cys (accessed [today's date]).

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