methylmalonic aciduria and homocystinuria type cblC
Findings
No curated finding names methylmalonic aciduria and homocystinuria type cblC yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
A form of methylmalonic acidemia with homocystinuria, an inborn error of vitamin B12 (cobalamin) metabolism characterized by megaloblastic anemia, lethargy, failure to thrive, developmental delay, intellectual deficit and seizures. cblC type methylmalonic acidemia with homocystinuria is caused by mutations in the MMACHC gene (1p36.3) and is transmitted in an autosomal recessive manner.
Definition from the Mondo Disease Ontology (MONDO:0010184), read 2026-09-29. CC BY 4.0.
- Inheritance
- Autosomal recessive inheritance
- Onset and course
- Infantile onset · Middle age onset · Juvenile onset · Neonatal onset · Young adult onset · Childhood onset
HPO, annotations 2026-09-02
Features
89 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.
- Decreased methionine synthase activityHPOHP:0003524
- 3 of 3 reported patients
- Decreased methylmalonyl-CoA mutase activityHPOHP:0003210
- 3 of 3 reported patients
- Elevated circulating palmitoleylcarnitine concentrationHPOHP:0031544
- Very frequent (80% to 99% of cases)
- HyperhomocystinemiaHPOHP:0002160
- 2 of 3 reported patients
- Very frequent (80% to 99% of cases)
- Intellectual disabilityHPOHP:0001249
- Very frequent (80% to 99% of cases)
Genes
2 genes
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.
- MMACHCHGNC:24525
- Definitive · ClinGen · Autosomal recessive · 2020
- Definitive · Myriad Women's Health · Autosomal recessive · 2018
- Definitive · G2P · Autosomal recessive · 2018
- Definitive · Natera · Autosomal recessive · 2023
- Strong · Ambry Genetics · Autosomal recessive · 2018
- Strong · Labcorp Genetics (formerly Invitae) · Autosomal recessive · 2023
- Strong · PanelApp Australia · Autosomal recessive · 2025
- Supportive · Orphanet · Autosomal recessive · 2021
- PRDX1HGNC:9352
- Strong · Labcorp Genetics (formerly Invitae) · Autosomal recessive · 2021
Where it sits
Other names
5 names
Resolves to: methylmalonic aciduria and homocystinuria type cblC
- Also called
- cblC defectcobalamin C defectcobalamin c diseasecombined defect in adenosylcobalamin and methylcobalamin synthesis, type cblCmethylmalonic aciduria with homocystinuria, type cblC