Homocystinuria

• Rare (incidence ~1 in 344,000) • Defect in cystathionine β-synthase (CBS) is the most common (defect in methionine synthase also possible) • Autosomal recessive disorders • Excess homocystine(oxidised form of homocysteine) excreted in urine • Accumulation of homocysteine and methionine causes disease symptoms