Is EXT2 p.Arg266= (c.798A>G) pathogenic?

EXT2 p.Arg266= (c.798A>G) is classified Likely benign in EXT2 (ClinVar, Single submitter, 1 submitter; last evaluated 2022-12-31). Very rare (popmax 0.00134%, afr); Associated with exostoses, multiple, type 2.

What condition is associated with EXT2 p.Arg266= (c.798A>G)?

EXT2 p.Arg266= (c.798A>G) is associated with exostoses, multiple, type 2 (ClinVar).

How common is EXT2 p.Arg266= (c.798A>G) in the general population?

EXT2 p.Arg266= (c.798A>G) is very rare (popmax 0.00134%, afr) (gnomAD).

How is Multiple osteochondromas inherited?

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

EXT2 p.Arg266=

c.798A>G · rs1189165037 · VCV2961192

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00134%, afr)

Conditions

exostoses, multiple, type 2

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 0.26	GERP -0.64, phastCons 0.35
Overall
CADD	10.01	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00134% African / African-American · 1/74,886 alleles

Overall 0.000124% 2/1,613,954 alleles · very rare exomes 1/1,461,866 · genomes 1/152,088 · joint denominator

Ancestry group	Frequency	1 in
African / African-Americangrpmax	0.00134%	74,886
European (non-Finnish)	8.47e-05%	1,180,018

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: EXT2
Protein: p.Arg266=
Coding: c.798A>G
MANE Select: NM_207122
dbSNP: rs1189165037
Type: single nucleotide variant
Location: chr11:44124843 (GRCh38)
Gene constraint: LOEUF 0.775 · pLI <0.01 · ClinGen HI 3/3 (gnomAD)
Structure: AlphaFold pLDDT 87.59 · 6 PDB
Residue 266: an α-helix

Full EXT2 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

exostoses, multiple, type 2 — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Multiple osteochondromas (Orphanet):

Inheritance: Autosomal dominant
Onset: Childhood
Prevalence: >1 / 1000 (Specific population)

Similar variants

EXT2 p.Arg266Ter Likely pathogenic ★ same residue
EXT2 c.1079+1G>A Pathogenic ★★ same condition
EXT2 c.1079+1G>T Pathogenic ★★ same condition
EXT2 c.1173+1G>A Pathogenic ★★ same condition
EXT2 c.1662+1G>C Likely pathogenic ★★ same condition
EXT2 c.536+1G>A Pathogenic ★★ same condition
EXT2 c.626+1G>A Pathogenic ★★ same condition
EXT2 c.626+1G>C 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/ext2-p-arg266 (accessed [today's date]).

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