Is PHKA2 p.Arg367Cys (c.1099C>T) pathogenic?

PHKA2 p.Arg367Cys (c.1099C>T) is classified Uncertain significance in PHKA2 (ClinVar, Single submitter, 1 submitter; last evaluated 2025-01-06). AlphaMissense: likely benign (0.0703); Very rare (popmax 0.00296%, eas); Associated with glycogen storage disease IXa1.

What condition is associated with PHKA2 p.Arg367Cys (c.1099C>T)?

PHKA2 p.Arg367Cys (c.1099C>T) is associated with glycogen storage disease IXa1 (ClinVar).

How common is PHKA2 p.Arg367Cys (c.1099C>T) in the general population?

PHKA2 p.Arg367Cys (c.1099C>T) is very rare (popmax 0.00296%, eas) (gnomAD).

What do computational predictors say about PHKA2 p.Arg367Cys (c.1099C>T)?

AlphaMissense predicts likely benign (score 0.0703) — an in-silico prediction, not a clinical call.

PHKA2 p.Arg367Cys

Q: How is Glycogen storage disease due to liver phosphorylase kinase deficiency inherited?

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

c.1099C>T · rs1287580250 · VCV948885

Uncertain significance Single submitter

Classification

Uncertain significance

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

AlphaMissense

likely benign

0.0703 · ACMG-weighted

gnomAD v4.1

Rare

very rare (popmax 0.00296%, eas)

Missense predictors

0/2 damaging

AlphaMissense, SaProt · REVEL indeterminate

Conditions

glycogen storage disease IXa1

Computational evidence

Protein change
AlphaMissense	0.0703	likely benign
REVEL	0.455	indeterminate
SaProt	LLR -9.48	tolerated
⇒ AlphaMissense and SaProt both call this tolerated; REVEL is indeterminate.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP 6.5	GERP -0.4, phastCons 1
Regional constraint	o/e 0.90	unconstrained · MANE · 45 kb · p 0.0065 · regional, not allelic
Overall
CADD	19.72	PHRED · no single calibrated threshold — expert panels disagree

ClinVar classifies this uncertain; the computational predictors unanimously lean tolerated — a triage signal, not a reclassification

AlphaMissense carries the ACMG weight for missense; REVEL and SaProt are independent agreement signals.

Population frequency

gnomAD v4.1 · exomes + genomes

Grpmax group 0.00296% East Asian · 1/33,806 alleles

Filtering AF 3.7e-05% ClinGen BA1/BS1 input FAF95, joint · FAF99 1.4e-05%

Overall 0.000331% 4/1,209,043 alleles · very rare exomes 4/1,095,698 · genomes 0/113,345 · joint denominator

Ancestry group	Frequency	1 in
East Asiangrpmax	0.00296%	33,806
Admixed American	0.00217%	46,009
European (non-Finnish)	0.000224%	446,648

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: PHKA2
Protein: p.Arg367Cys
Coding: c.1099C>T
MANE Select: NM_000292
dbSNP: rs1287580250
Type: single nucleotide variant
Location: chrX:18936093 (GRCh38)
Structure: AlphaFold pLDDT 81.36

Full PHKA2 gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

glycogen storage disease IXa1 — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Glycogen storage disease due to liver phosphorylase kinase deficiency (Orphanet):

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

Similar variants

PHKA2 p.Arg367His Likely benign ★ same residue
PHKA2 c.1325-2A>G Likely pathogenic ★★ same condition
PHKA2 c.2597+1G>A Pathogenic/Likely pathogenic ★★ same condition
PHKA2 c.537+2T>C Pathogenic/Likely pathogenic ★★ same condition
PHKA2 c.918+1G>A Pathogenic/Likely pathogenic ★★ same condition
PHKA2 p.Arg1111Ter Pathogenic ★★ same condition
PHKA2 p.Arg186Cys Pathogenic/Likely pathogenic ★★ same condition
PHKA2 p.Arg186His Likely 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/phka2-p-arg367cys (accessed [today's date]).

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