Is MMAB p.Ala2= (c.6T>A) pathogenic?

MMAB p.Ala2= (c.6T>A) is classified Likely benign in MMAB (ClinVar, Single submitter, 1 submitter; last evaluated 2022-05-27). Absent from gnomAD v4.1; Associated with methylmalonic aciduria, cblB type.

What condition is associated with MMAB p.Ala2= (c.6T>A)?

MMAB p.Ala2= (c.6T>A) is associated with methylmalonic aciduria, cblB type (ClinVar).

How common is MMAB p.Ala2= (c.6T>A) in the general population?

MMAB p.Ala2= (c.6T>A) 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.Ala2=

c.6T>A · rs2548614506 · VCV1999651

Likely benign Single submitter

Classification

Likely benign

ClinVar

Review

Single submitter ★☆☆☆

ClinVar · 1 submitter

gnomAD v4.1

Not reported

no allele count reported in gnomAD v4.1 (AN 1,603,232)

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 0.15	GERP 1.8
Overall
CADD	10.31	PHRED · no single calibrated threshold — expert panels disagree

Population frequency

gnomAD v4.1 · exomes + genomes

No allele count reported in gnomAD v4.1 (AN 1,603,232). 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: MMAB
Protein: p.Ala2=
Coding: c.6T>A
MANE Select: NM_052845
dbSNP: rs2548614506
Type: single nucleotide variant
Location: chr12:109573475 (GRCh38)
Gene constraint: LOEUF 0.874 · pLI <0.01 · ClinGen HI gene assoc. with recessive phenotype (gnomAD)
Structure: AlphaFold pLDDT 82.39 · 6 PDB

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.Ala2Val Uncertain significance ★ ⚠ same residue
MMAB c.197-1G>T Pathogenic ★★ same condition
MMAB c.290+1G>A Likely pathogenic ★★ same condition
MMAB c.291-1G>A Pathogenic ★★ same condition
MMAB c.349-1G>C Pathogenic/Likely pathogenic ★★ same condition
MMAB c.584+2T>C Likely pathogenic ★★ same condition
MMAB p.Arg186Gln Pathogenic/Likely pathogenic ★★ same condition
MMAB p.Arg186Pro 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-ala2 (accessed [today's date]).

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