• Turnaround time:
    10–21 calendar days (14 days on average)
  • Preferred specimen:
    3mL whole blood in a purple-top tube
  • Alternate specimens:
    DNA or saliva/assisted saliva
  • Sample requirements
  • Request a sample kit



ATR; CFAP23; cblB; cob

Associated disorders

The MMAB gene is associated with autosomal recessive cobalamin B type methylmalonic aciduria (MedGen UID: 344420).

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Invitae tests that include this gene:

An estimated 12% of isolated methylmalonic acidemia cases are due to pathogenic variants in the MMAB gene (PMID: 17597648).

The MMAB gene encodes the cobalamin B enzyme, which is involved in the metabolism of cobalamin (vitamin B12) to one of its active forms, adenosylcobalamin. Adenosylcobalamin is a cofactor for the methylmalonyl-CoA mutase enzyme, which converts methylmalonyl-CoA to succinyl-CoA, a component of the Krebs cycle. Pathogenic variants in MMAB lead to decreased function of the methylmalonyl-CoA mutase enzyme, which results in toxic accumulation of methylmalonic acid in the body (PMID: 24813872).

Assay and technical information

Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology (NGS).

Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence in the transcript listed below. In addition, analysis covers the select non-coding variants specifically defined in the table below. Any variants that fall outside these regions are not analyzed. Any specific limitations in the analysis of these genes are also listed in the table below.

Our analysis detects most intragenic deletions and duplications at single exon resolution. However, in rare situations, single-exon copy number events may not be analyzed due to inherent sequence properties or isolated reduction in data quality. If you are requesting the detection of a specific single-exon copy number variation, please contact Client Services before placing your order.

Gene Transcript reference Sequencing analysis Deletion/Duplication analysis
MMAB NM_052845.3