Is F9 p.Ile428= (c.1284T>C) pathogenic?

F9 p.Ile428= (c.1284T>C) is classified Likely benign in F9 (ClinVar, Single submitter, 1 submitter; last evaluated 2023-01-08). Very rare (popmax 0.00175%, afr); Associated with thrombophilia, X-linked, due to factor 9 defect.

What condition is associated with F9 p.Ile428= (c.1284T>C)?

F9 p.Ile428= (c.1284T>C) is associated with thrombophilia, X-linked, due to factor 9 defect, hemophilia B (ClinVar).

How common is F9 p.Ile428= (c.1284T>C) in the general population?

F9 p.Ile428= (c.1284T>C) is very rare (popmax 0.00175%, afr) (gnomAD).

F9 p.Ile428=

c.1284T>C · rs1300185736 · VCV1145995

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00175%, afr)

Conditions

thrombophilia, X-linked, due to factor 9 defect

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 0.62	GERP 2.8, phastCons 1
Overall
CADD	6.928	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00175% African / African-American · 1/57,152 alleles

Filtering AF 0.000565% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.000412%

Overall 0.000909% 11/1,209,606 alleles · very rare exomes 9/1,097,632 · genomes 2/111,974 · joint denominator

Ancestry group	Frequency	1 in
African / African-Americangrpmax	0.00175%	57,152
European (non-Finnish)	0.00112%	89,485

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: F9
Protein: p.Ile428=
Coding: c.1284T>C
MANE Select: NM_000133
dbSNP: rs1300185736
Type: single nucleotide variant
Location: chrX:139561969 (GRCh38)
Structure: AlphaFold pLDDT 80.45 · 57 PDB
Residue 428: a β-strand; the peptidase s1 domain

Full F9 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

thrombophilia, X-linked, due to factor 9 defect — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Also linked: hemophilia B

Similar variants

F9 p.Ile428Phe Likely pathogenic ★ same residue
F9 c.520+13A>G Pathogenic ★★★ same condition
F9 c.88+1G>A Pathogenic ★★★ same condition
F9 c.88+5G>T Likely pathogenic ★★★ same condition
F9 p.Ala279Thr Pathogenic ★★★ ⚠ same condition
F9 p.Ala337Pro Likely pathogenic ★★★ same condition
F9 p.Ala337Thr Pathogenic ★★★ ⚠ same condition
F9 p.Ala337Val 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/f9-p-ile428 (accessed [today's date]).

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