|
Alternative names
|
- Methylmalonyl-CoA mutase deficiency
- Cbl E, Cbl G, Cbl D1, MTHFR deficiency
|
|
About the condition
|
Remethylation disorders are organic acid disorders. They are a group of hereditary diseases that are caused by a missing enzyme needed for metabolism of methionine and homocysteine. The disorders can also result from deficiency of the cobalamin cofactors required by the enzymes.
|
|
Inheritance
|
Autosomal recessive
|
|
Year screening started in WA
|
2019
|
|
Incidence in Australia
|
Currently unknown
|
|
Enzyme defect
|
- Defect in methionine synthase or methylcobalamin cofactor
- At least four distinct biochemical causes of this disorder have been identified
|
|
Symptoms if untreated
|
- Intellectual disability
- Seizures, encephalopathy
- Thromoboembolism, vascular disease
- Megaloblastic anaemia
- Later-onset and milder forms occur
|
|
Metabolites on bloodspot screening
|
- Decreased methionine
- Increased homocysteine (second-tier test)
|
|
Diagnostic tests
|
- Plasma amino acid profile
- Urine organic acids
- Plasma total homocysteine
- Vitamin B12, folate
- Homocysteinaemia gene panel
|
|
Treatment
|
- Low-protein diet
- Vitamin B12 B6, B2, betaine, folic or folinic acid (dependent on defect)
- Carnitine supplementation
|
|
Screening issues
|
- Screening may incidentally detect vitamin B12 deficiency
- Later-onset and milder variants may not be detected
|