Is CA5A p.Arg26His (c.77G>A) pathogenic?

CA5A p.Arg26His (c.77G>A) is classified Uncertain significance in CA5A (ClinVar, Multiple submitters, 2 submitters; last evaluated 2023-03-06). AlphaMissense: likely benign (0.0707); Very rare (popmax 0.00585%, nfe); Associated with hyperammonemic encephalopathy due to carbonic anhydrase VA deficiency.

What condition is associated with CA5A p.Arg26His (c.77G>A)?

CA5A p.Arg26His (c.77G>A) is associated with hyperammonemic encephalopathy due to carbonic anhydrase VA deficiency (ClinVar).

How common is CA5A p.Arg26His (c.77G>A) in the general population?

CA5A p.Arg26His (c.77G>A) is very rare (popmax 0.00585%, nfe) (gnomAD).

What do computational predictors say about CA5A p.Arg26His (c.77G>A)?

AlphaMissense predicts likely benign (score 0.0707) — an in-silico prediction, not a clinical call.

CA5A p.Arg26His

Q: How is Hyperammonemic encephalopathy due to carbonic anhydrase VA deficiency inherited?

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

c.77G>A · rs368273900 · VCV2067315

Uncertain significance Multiple submitters

Classification

Uncertain significance

ClinVar

Review

Multiple submitters ★★☆☆

ClinVar · 2 submitters

AlphaMissense

likely benign

0.0707 · ACMG-weighted

gnomAD v4.1

Rare

very rare (popmax 0.00585%, nfe)

Missense predictors

0/3 damaging

AlphaMissense, REVEL, SaProt

Conditions

hyperammonemic encephalopathy due to carbonic anhydrase VA deficiency

Computational evidence

Protein change
AlphaMissense	0.0707	likely benign
REVEL	0.035	moderately benign-leaning
SaProt	LLR -8.09	tolerated
⇒ AlphaMissense, REVEL and SaProt all call this tolerated.
Splicing
SpliceAI	—	not assessed · no allele here is in the release
Constraint at this position
Conservation	phyloP -6.6	GERP -2.5
Regional constraint	o/e 1.11	unconstrained · MANE · 48 kb · p 0.027 · regional, not allelic
Overall
CADD	0.13	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 0.00585% European (non-Finnish) · 69/1,179,964 alleles

Filtering AF 0.0047% ClinGen BA1/BS1 input FAF95, joint · FAF99 0.00431%

Overall 0.00465% 75/1,613,866 alleles · very rare

Ancestry group	Frequency	1 in
European (non-Finnish)grpmax	0.00585%	17,101
African / African-American	0.00534%	18,718
Remaining individualsnot grpmax-eligible	0.0016%	62,474
South Asian	0.0011%	91,078

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: CA5A
Protein: p.Arg26His
Coding: c.77G>A
MANE Select: NM_001739
dbSNP: rs368273900
Type: single nucleotide variant
Location: chr16:87936374 (GRCh38)
Gene constraint: LOEUF 1.257 · pLI <0.01 (gnomAD)
Structure: AlphaFold pLDDT 84.38

Full CA5A gene report on Sugi Atlas → Gene function, pathways, protein structure, interactions & more

Disease context

hyperammonemic encephalopathy due to carbonic anhydrase VA deficiency — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Hyperammonemic encephalopathy due to carbonic anhydrase VA deficiency (Orphanet):

Inheritance: Autosomal recessive
Onset: Childhood, Infancy, Neonatal

Similar variants

CA5A p.Arg32Ter Pathogenic ★★ same condition
CA5A p.Glu241Lys Pathogenic/Likely pathogenic ★★ same condition
CA5A p.Ala149Thr Uncertain significance ★★ ⚠ same condition
CA5A p.Ala208Val Uncertain significance ★★ ⚠ same condition
CA5A p.Ala261Val Uncertain significance ★★ ⚠ same condition
CA5A p.Asp216Ala Uncertain significance ★★ ⚠ same condition
CA5A p.Gln79Glu Uncertain significance ★★ ⚠ same condition
CA5A p.His143Asp 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/ca5a-p-arg26his (accessed [today's date]).

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