Is AMN p.Trp221Ter (c.663G>A) pathogenic?

AMN p.Trp221Ter (c.663G>A) is classified Pathogenic in AMN (ClinVar, Single submitter, 2 submitters; last evaluated 2023-03-02). Absent from gnomAD v4.1; Associated with Imerslund-Grasbeck syndrome.

What condition is associated with AMN p.Trp221Ter (c.663G>A)?

AMN p.Trp221Ter (c.663G>A) is associated with Imerslund-Grasbeck syndrome (ClinVar).

How common is AMN p.Trp221Ter (c.663G>A) in the general population?

AMN p.Trp221Ter (c.663G>A) is absent from gnomAD v4.1 (gnomAD).

How is Imerslund-Gräsbeck syndrome inherited?

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

AMN p.Trp221Ter

c.663G>A · rs386834174 · VCV56756

Pathogenic Single submitter

Classification

Pathogenic

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 2 submitters

Consequence

nonsense (stop-gain)

predicted LoF

gnomAD v4.1

Not reported

no allele count reported in gnomAD v4.1 (AN 1,531,084)

Conditions

Imerslund-Grasbeck syndrome

Computational evidence

Protein change
Missense predictors do not apply to this variant type; conservation carries the signal.
Consequence	nonsense (stop-gain)	predicted loss-of-function
NMD	predicted	premature termination codon in exon 7 of 12
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 8.7	GERP 0.93, phastCons 1
Overall
CADD	37.0	PHRED · no single calibrated threshold — expert panels disagree

Predicted loss-of-function is descriptive, not an applied PVS1 code.

Population frequency

gnomAD v4.1 · exomes + genomes

No allele count reported in gnomAD v4.1 (AN 1,531,084). This is missing data, not an absence: the variant may or may not be present in gnomAD. Rarity (ACMG PM2) and BA1/BS1 cannot be assessed for it.

Variant & gene context

Gene: AMN
Protein: p.Trp221Ter
Coding: c.663G>A
MANE Select: NM_030943
dbSNP: rs386834174
Type: single nucleotide variant
Location: chr14:102929439 (GRCh38)
Gene constraint: LOEUF 1.446 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 80.78 · 1 PDB
Residue 221: an α-helix; the vwfc domain

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

Disease context

Imerslund-Grasbeck syndrome — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Imerslund-Gräsbeck syndrome (Orphanet):

Inheritance: Autosomal recessive
Onset: Childhood
Prevalence: 1-9 / 1 000 000 (Finland)

Similar variants

AMN c.208-1G>C Pathogenic/Likely pathogenic ★★ same condition
AMN c.296-1G>A Likely pathogenic ★★ same condition
AMN c.44-1G>A Likely pathogenic ★★ same condition
AMN c.760+1G>A Likely pathogenic ★★ same condition
AMN c.844-1G>C Likely pathogenic ★★ same condition
AMN p.Thr41Ile Likely pathogenic ★★ ⚠ same condition
AMN p.Trp391Ter Pathogenic/Likely pathogenic ★★ same condition
AMN c.296-3C>T Uncertain significance ★★ 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/amn-p-trp221ter (accessed [today's date]).

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