Is F9 p.His303= (c.909C>T) pathogenic?

F9 p.His303= (c.909C>T) is classified Likely benign in F9 (ClinVar, Single submitter, 1 submitter; last evaluated 2021-03-17). Very rare (popmax 0.00296%, eas); Associated with hemophilia B.

What condition is associated with F9 p.His303= (c.909C>T)?

F9 p.His303= (c.909C>T) is associated with hemophilia B, thrombophilia, X-linked, due to factor 9 defect (ClinVar).

How common is F9 p.His303= (c.909C>T) in the general population?

F9 p.His303= (c.909C>T) is very rare (popmax 0.00296%, eas) (gnomAD).

How is Hemophilia B inherited?

Typically X-linked recessive (Orphanet). A genetic counselor can assess individual risk for a family.

F9 p.His303=

c.909C>T · rs2148367681 · VCV1529961

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Rare

very rare (popmax 0.00296%, eas)

Conditions

hemophilia B

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 -0.82	GERP 1.2
Overall
CADD	5.116	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00296% East Asian · 1/33,799 alleles

Overall 9.14e-05% 1/1,094,606 alleles · very rare

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.His303=
Coding: c.909C>T
MANE Select: NM_000133
dbSNP: rs2148367681
Type: single nucleotide variant
Location: chrX:139561594 (GRCh38)
Structure: AlphaFold pLDDT 80.45 · 57 PDB
Residue 303: a turn; a disulfide bond; the peptidase s1 domain

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

Disease context

hemophilia B — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Also linked: thrombophilia, X-linked, due to factor 9 defect

For Hemophilia B (Orphanet):

Inheritance: X-linked recessive
Onset: Childhood, Infancy, Neonatal
Prevalence: 1-9 / 100 000 (Europe)

Similar variants

F9 p.His303Tyr Benign/Likely benign ★★ 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-his303 (accessed [today's date]).

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