methylcobalamin deficiency type cblG
Findings
No curated finding names methylcobalamin deficiency type cblG yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
Methylcobalamin deficiency cbl G type is a rare condition that occurs when the body is unable to process certain amino acids (building blocks of protein) properly. In most cases, signs and symptoms develop during the first year of life; however, the age of onset can range from infancy to adulthood. Common features of the condition include feeding difficulties, lethargy, seizures, poor muscle tone (hypotonia), developmental delay, microcephaly (unusually small head size), and megaloblastic anemia. Methylcobalamin deficiency cbl G type is caused by changes (mutations) in the MTR gene and is inherited in an autosomal recessive manner. Treatment generally includes regular doses of hydroxycobalamin (vitamin B12). Some affected people may also require supplementation with folates and betaine.
Definition from the Mondo Disease Ontology (MONDO:0009609), read 2026-09-29. CC BY 4.0.
- Inheritance
- Autosomal recessive inheritance
- Onset and course
- Infantile onset · Neonatal onset
HPO, annotations 2026-09-02
Features
29 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
- 2 of 2 reported patients
- Global developmental delayHPOHP:0001263
- 1 of 1 reported patient
- HomocystinuriaHPOHP:0002156
- 3 of 3 reported patients
- HyperhomocystinemiaHPOHP:0002160
- 3 of 3 reported patients
- HypomethioninemiaHPOHP:0003658
- 5 of 5 reported patients
- LethargyHPOHP:0001254
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.
- MTRHGNC:7468
- Definitive · ClinGen · Autosomal recessive · 2021
- Definitive · G2P · Autosomal recessive · 2017
- Strong · Labcorp Genetics (formerly Invitae) · Autosomal recessive · 2018
- Strong · PanelApp Australia · Autosomal recessive · 2025
- Supportive · Orphanet · Autosomal recessive · 2021
Where it sits
Other names
1 name
Resolves to: methylcobalamin deficiency type cblG
- Also called
- functional methionine synthase deficiency type cblG