methylmalonic acidemia due to transcobalamin receptor defect
Findings
No curated finding names methylmalonic acidemia due to transcobalamin receptor defect yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
Methylmalonic aciduria due to transcobalamin receptor defect is a rare metabolite absorption and transport disorder characterized by a moderate increase of methylmalonic acid (MMA) in the blood and urine due to decreased cellular uptake of cobalamin resulting from decreased transcobalamin receptor function. Patients are usually asymptomatic however, screening reveals increased C3-acylcarnitine and MMA in plasma. Serum homocysteine levels may vary from normal to moderately elevated and retinal vascular occlusive disease, resulting in severe visual loss, has been reported.
Definition from the Mondo Disease Ontology (MONDO:0013341), read 2026-09-29. CC BY 4.0.
- Inheritance
- Autosomal recessive inheritance
- Onset and course
- Congenital onset · Infantile onset · Neonatal onset
HPO, annotations 2026-09-02
Features
4 features
What the disease is reported to present with, and how often among people who have it — never how often a feature means the disease. HPO, annotations 2026-09-02.
- Methylmalonic acidemiaHPOHP:0002912
- 1 of 1 reported patient
- Methylmalonic aciduriaHPOHP:0012120
- 1 of 1 reported patient · Neonatal onset
- 1 of 1 reported patient
- Reduced cellular cobalamin uptakeHPOHP:0034985
- 4 of 4 reported patients
- HyperhomocystinemiaHPOHP:0002160
- 1 of 2 reported patients
Genes
1 gene
Germline variants in the gene encoding each protein, as classified by GenCC submitters, each in their own words. Limited, disputed and refuted submissions are listed too.
- CD320HGNC:16692
- Definitive · ClinGen · Autosomal recessive · 2022
- Supportive · Orphanet · Autosomal recessive · 2021
- Limited · Ambry Genetics · Autosomal recessive · 2022
- Limited · Labcorp Genetics (formerly Invitae) · Unknown · 2020
- Limited · Laboratory for Molecular Medicine · Unknown · 2020
Where it sits
Other names
5 names
Resolves to: methylmalonic acidemia due to transcobalamin receptor defect
- Also called
- CD320 methylmalonic acidemiamethylmalonic acidemia caused by mutation in CD320methylmalonic acidemia, TCb1R typemethylmalonic acidemia, TCbIR typemethylmalonic aciduria due to transcobalamin receptor defect