Metabolic disorder is caused by a gene defect, environmental factors or an unknown aetiology. Altered metabolism caused by these factors affects normal function of various organs including the brain and may lead to abnormal phenotype. Understanding agents of causing these abnormalities is useful to interpret possible targets in these diseases. This book reveals what factors contribute in lysosomal storage diseases, Phenylketonuria and Canavan disease, as they are major emerging diseases in multiethnic populations.