CBS mutation screen

Cystathionine b-Synthase deficiency is an autosomal recessive disorder resulting in homocystinuria - the most common inborn error of methionine metabolism. CBS deficiency results in elevated levels of homocysteine and methionine. The world-wide frequency is reported as ~1:300000 but is highly variable with frequencies as high as 1:65000 in Ireland and 1:20500 in Denmark and as low as 1:800000 in Japan. Causative mutations in the CBS gene are heterogeneous but there are recurrent mutations including the 'Celtic mutation' p.Gly307Ser, responsible for >70% of alleles in patients of celtic origin, and the pan-ethnic p.Ile278Thr, identified in nearly 25% of all CBS alleles.