Is APOB p.Phe661Val (c.1981T>G) pathogenic?

APOB p.Phe661Val (c.1981T>G) is classified Uncertain significance in APOB (ClinVar, Single submitter, 1 submitter; last evaluated 2024-07-11). AlphaMissense: likely pathogenic (0.6017); Absent from gnomAD v4.1; Associated with familial hypobetalipoproteinemia 1.

What condition is associated with APOB p.Phe661Val (c.1981T>G)?

APOB p.Phe661Val (c.1981T>G) is associated with familial hypobetalipoproteinemia 1, hypercholesterolemia, autosomal dominant, type B (ClinVar).

How common is APOB p.Phe661Val (c.1981T>G) in the general population?

APOB p.Phe661Val (c.1981T>G) is absent from gnomAD v4.1 (gnomAD).

What do computational predictors say about APOB p.Phe661Val (c.1981T>G)?

AlphaMissense predicts likely pathogenic (score 0.6017) — an in-silico prediction, not a clinical call.

APOB p.Phe661Val

c.1981T>G · rs1663775549 · VCV1435378

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely pathogenic

0.6017 · ACMG-weighted

gnomAD v4.1

Absent

absent from gnomAD v4.1

Missense predictors

2/2 damaging

AlphaMissense, REVEL · SaProt no call

Conditions

familial hypobetalipoproteinemia 1

Computational evidence

Protein change
AlphaMissense	0.6017	likely pathogenic · top 8% in APOB
REVEL	0.761	pathogenic-leaning
SaProt	—	not scored · why
⇒ AlphaMissense and REVEL both call this damaging; SaProt makes no call.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 9.4	GERP 1.9, phastCons 1
Regional constraint	o/e 1.00	unconstrained · MANE · 32 kb · p 0.91 · regional, not allelic
Overall
CADD	25.7	PHRED · no single calibrated threshold — expert panels disagree

ClinVar classifies this uncertain; the computational predictors unanimously lean damaging — 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

Absent from gnomAD v4.1. Not observed in any sequenced alleles — a rarity signal (ACMG PM2-supporting), not evidence of pathogenicity on its own.

Variant & gene context

Gene: APOB
Protein: p.Phe661Val
Coding: c.1981T>G
MANE Select: NM_000384
dbSNP: rs1663775549
Type: single nucleotide variant
Location: chr2:21027914 (GRCh38)
Gene constraint: LOEUF 0.537 · pLI <0.01 · ClinGen HI 3/3 (gnomAD)
Residue 661: the vitellogenin domain

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

Disease context

familial hypobetalipoproteinemia 1 — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

Also linked: hypercholesterolemia, autosomal dominant, type B

Similar variants

APOB p.Phe661= Likely benign ★ same residue
APOB c.1830-1G>A Pathogenic ★★ same condition
APOB c.2604+1G>A Likely pathogenic ★★ same condition
APOB c.537+1G>T Pathogenic/Likely pathogenic ★★ same condition
APOB p.Arg1333Ter Pathogenic ★★ same condition
APOB p.Arg2012Ter Pathogenic ★★ same condition
APOB p.Arg2085Ter Pathogenic/Likely pathogenic ★★ same condition
APOB p.Arg2513Ter 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/apob-p-phe661val (accessed [today's date]).

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