Homocystinuria

Rare inherited disorder of methionine metabolism. Homocysteine accumulates from birth and damages vessels, skeleton, lens and nervous system. Treatment is lifelong: methionine-restricted diet, vitamin B6, folate, B12 and betaine for the alternative remethylation pathway.

ICD-10 E72.11 drug

Also known as: Cystathionine beta-synthase deficiency, Classical homocystinuria, CBS deficiency

Drugs used for this condition

ABetaine (trimethylglycine, TMG)First line · Methyl donor; agent for the alternative homocysteine remethylation pathwayBetaine (Cystadane) is first-line treatment for classical homocystinuria and for methyltetrahydrofolate reductase deficiency or B12-dependent remethylation defects in children and adults. FDA approved the drug in 1996; AEMPS confirms the indication. Dose: 100 mg/kg/day split into two intakes, titrated to plasma homocysteine below 15 µmol/L. Therapy is lifelong under a metabolic paediatrician and regular plasma amino-acid panels. There is no alternative regimen.

How to read tiers A–F

Evidence tiers belong to the drug-indication pair, not to the drug as a whole: the same substance can be A for one condition and F for another.

AStrong evidence – first or second line in international guidelines
BRecommended in selected cases
CStudy data contradict each other
DBenefit not proven, no documented harm
FDocumented harm, or risk without benefit