Gene therapy and mRNA-based approaches in preclinical development
Liver transplantation: curative but associated with surgical risk and immunosuppression burden
ICD-10 coding
E72.11: Homocystinuria (CBS deficiency is primary code)
E72.19: Other disorders of sulfur-bearing amino acid metabolism
SNOMED CT: 54365001 (Homocystinuria)
Patient Discharge Instructions
copy discharge instructions
Diagnosis and condition overview
Homocystinuria is a rare inherited metabolic condition where a substance called homocysteine builds up in your blood
This can cause blood clots, eye problems, bone problems, and in some cases developmental issues
With careful treatment, most complications can be prevented
Medications — take exactly as prescribed
Pyridoxine (vitamin B6): take every day as directed; do not skip doses
This helps lower homocysteine levels in patients whose body responds to B6
Betaine (Cystadane): take with meals; dose adjustments must only be made by your metabolic doctor
Too high a dose can cause a dangerous chemical called methionine to rise; do not self-adjust dose
Folic acid and vitamin B12: take as directed; important for homocysteine metabolism
Do not take any new medications, supplements, or herbal products without checking with your metabolic team
Diet instructions
Follow your low-methionine diet strictly; your dietitian will provide a specific meal plan
Take your amino acid formula as prescribed; this replaces the protein you are restricting
Drink plenty of fluids every day — at least 8 glasses of water
Activity and prevention
Avoid long periods of sitting or lying still without moving (blood clots can form)
During long car rides or flights, stand and walk every 1–2 hours
Move your legs frequently if you cannot walk
If you are having surgery or a procedure, make sure the anesthesia team knows you have homocystinuria
Nitrous oxide (laughing gas) must NOT be used; it is harmful to people with your condition
Do not use birth control pills if you are female with homocystinuria (increases clot risk)
Ask your doctor about safe contraception options
When to return to emergency immediately
Sudden weakness or numbness in arm or leg, face drooping, speech difficulty (stroke)
Sudden severe headache unlike any before
Sudden blurred vision or loss of vision in one eye (possible lens dislocation)
Leg or arm that is swollen, red, warm, and painful (blood clot in vein)
Chest pain or sudden shortness of breath (blood clot in lung)
Confusion or unusual behavior
Follow-up appointments
Keep all appointments with your metabolic genetics specialist and dietitian
Regular blood tests to check homocysteine and methionine levels are essential
See your eye doctor at least once per year
Bone density scan every 3–5 years starting in adolescence
References
Guidelines and key sources
Sacharow SJ, Levy HL. Homocystinuria due to Cystathionine Beta-Synthase Deficiency
GeneReviews, NCBI Bookshelf, 2025
Primary evidence source for clinical presentation, diagnosis, and management
Morris AAM, Sokolova J, Pavlikova M, et al. Cystathionine Beta-Synthase Deficiency in the E-HOD Registry Part II: Dietary and Pharmacological Treatment
Journal of Inherited Metabolic Disease, 2025
European prospective registry; real-world treatment outcomes
Walter JH, Jahnke N, Remmington T. Newborn Screening for Homocystinuria
Cochrane Database of Systematic Reviews, 2015
NBS evidence; treated vs untreated outcome comparisons
Testai FD, Gorelick PB. Inherited Metabolic Disorders and Stroke Part 2: Homocystinuria, Organic Acidurias, and Urea Cycle Disorders
Archives of Neurology (JAMA Neurology), 2010
Stroke risk and management in HCU
Mandel H, Brenner B, Berant M, et al. Coexistence of Hereditary Homocystinuria and Factor V Leiden — Effect on Thrombosis
New England Journal of Medicine, 1996
Landmark study on compounding thrombotic risk
Kluijtmans LA, Boers GH, Kraus JP, et al. The Molecular Basis of Cystathionine Beta-Synthase Deficiency in Dutch Patients
American Journal of Human Genetics, 1999
Genotype-phenotype correlation; I278T and G307S mutation characterization
Gerrard A, Dawson C. Homocystinuria Diagnosis and Management: It Is Not All Classical
Kozich V, Majtan T. Molecular Basis of Phenotype Expression in Homocystinuria: Where Are We 30 Years Later?
Journal of Inherited Metabolic Disease, 2024
Current understanding of molecular mechanisms and emerging therapies
Welch GN, Loscalzo J. Homocysteine and Atherothrombosis
New England Journal of Medicine, 1998
Foundational paper on vascular toxicity mechanisms of homocysteine
Althubity AA. Homocystinuria: Advances in Metabolic and Molecular Therapies Targeting Homocysteine Pathways
Molecular Medicine Reports, 2026
Review of emerging therapeutic approaches including enzyme replacement and gene therapy
De Biase I, Gherasim C, La'ulu SL, et al. Laboratory Evaluation of Homocysteine Remethylation Disorders and Classic Homocystinuria
Clinica Chimica Acta, 2020
Long-term laboratory follow-up in 123 patients; biochemical differentiation of disorders
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.