Adjunctive treatment of homocystinuria, involving deficiencies or defects in: cystathionine beta-synthase (CBS); 5,10-methylene-tetrahydrofolate reductase (MTHFR); cobalamin cofactor metabolism (cbl). Cystadane should be used as supplement to other therapies such as vitamin B6 (pyridoxine), vitamin B12 (cobalamin), folate and a specific diet.