Cystathionine beta synthase deficiency
Genetic counseling is recommended for prospective parents with a family history of homocystinuria. Intrauterine diagnosis of homocystinuria is available. This involves culturing amniotic cells or chorionic villi to test for cystathionine synthase (the enzyme that is missing in homocystinuria).
Rezvani I. Defects in Metabolism of Amino Acids. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF. Kliegman: Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 85.