Traits

Traits linked to MMAB

metabolism of cobalamin associated B

The Human Phenotype Ontology links 29 traits to MMAB, by body system: features seen in people with one of the gene's rare conditions.

Laboratory abnormality

Trait	How often it is seen
Decreased methylmalonyl-CoA mutase activity	Always
Elevated circulating methylmalonylcarnitine concentration	Always
Elevated circulating propionylcarnitine concentration	Always
High blood ammonia levels	Always
Low blood sugar	Always
Methylmalonic acidemia	Always
Methylmalonic aciduria	Always
Decreased circulating adenosylcobalamin concentration	Very often (80–99%)
Dehydration	Not recorded
Elevated blood glycine levels	Not recorded
High levels of ketone bodies	Not recorded
Ketonuria	Not recorded
Metabolic acidosis	Not recorded

Abnormality of the nervous system

Trait	How often it is seen
Delayed motor skills	Always
Persistent head lag	Always
Coma	Not recorded
Global developmental delay	Not recorded
Lethargy	Not recorded

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Low blood cell count	Not recorded
Low blood neutrophil count	Not recorded
Low number of red blood cells or hemoglobin	Not recorded
Low platelet count	Not recorded

Abnormality of the digestive system

Trait	How often it is seen
Enlarged liver	Not recorded
Feeding difficulties in infancy	Not recorded
Vomiting	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Stretched and thinned heart muscle	Always

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone	Always

Abnormality of the respiratory system

Trait	How often it is seen
Breathing difficulties	Not recorded

Growth abnormality

Trait	How often it is seen
Faltering weight	Not recorded

How often is among people with one of the gene's conditions, the most often across them, as the Human Phenotype Ontology records it. These pages describe traits and the research behind them; they are not a diagnosis, and a doctor or genetic counsellor is the person to ask about symptoms.

Where this comes from

The Human Phenotype Ontology, release 2026-09-01: the traits linked to MMAB and how often each is seen. Find out more at hpo.jax.org.

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