Is MMAB p.Arg191= (c.573G>C) pathogenic?

MMAB p.Arg191= (c.573G>C) is classified Likely benign in MMAB (ClinVar, Single submitter, 1 submitter; last evaluated 2021-03-01). Absent from gnomAD v4.1; Associated with methylmalonic aciduria, cblB type.

What condition is associated with MMAB p.Arg191= (c.573G>C)?

MMAB p.Arg191= (c.573G>C) is associated with methylmalonic aciduria, cblB type (ClinVar).

How common is MMAB p.Arg191= (c.573G>C) in the general population?

MMAB p.Arg191= (c.573G>C) is absent from gnomAD v4.1 (gnomAD).

How is Vitamin B12-responsive methylmalonic acidemia inherited?

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

MMAB p.Arg191=

c.573G>C · rs2136198226 · VCV1537956

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Absent

absent from gnomAD v4.1

Conditions

methylmalonic aciduria, cblB type

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 -2.3	GERP -3.8
Overall
CADD	1.319	PHRED · no single calibrated threshold — expert panels disagree

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: MMAB
Protein: p.Arg191=
Coding: c.573G>C
MANE Select: NM_052845
dbSNP: rs2136198226
Type: single nucleotide variant
Location: chr12:109561051 (GRCh38)
Gene constraint: LOEUF 0.874 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 82.39 · 6 PDB
Residue 191: a UniProt-annotated variant site (in macb); an α-helix; a binding site

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

Disease context

methylmalonic aciduria, cblB type — disease report on Sugi Atlas → Associated genes, phenotypes, clinical trials & treatments

For Vitamin B12-responsive methylmalonic acidemia (Orphanet):

Inheritance: Autosomal recessive
Onset: Childhood

Similar variants

MMAB p.Arg191Gln Pathogenic ★★ ⚠ same residue
MMAB p.Arg191Trp Pathogenic ★★ same residue
MMAB p.Arg191Gly Likely pathogenic ★ same residue
MMAB p.Arg191Pro Likely pathogenic ★ same residue
MMAB p.Arg191dup Likely pathogenic ★★ same residue
MMAB p.Arg191fs Likely pathogenic ★ same residue
MMAB c.197-1G>T Pathogenic ★★ same condition
MMAB c.290+1G>A 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/mmab-p-arg191 (accessed [today's date]).

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