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