Inborn Errors of Metabolism
Inborn errors of metabolism is the name given to a number of diseases involving defective enzyme mechanisms, many of which if untreated can affect brain function and delay development. Of the hundreds that have been identified, phenylketonuria is one of the most common, affecting between one and two in every 20,000 births. It is caused by a defect in the enzyme responsible for the breakdown of the substance phenylalanine, which is present in our diets. It may be detected by a blood test before birth. Treatment is by dietary manipulation.
Homocysteinuria is a rarer syndrome due to a defect in the breakdown of homocysteine, a chemical involved in the synthesis of the amino acids. Besides mental retardation there are defects in the skeleton and in the lens of the eye. Disorders in the breakdown of our amino acids produce a number of diseases such as maple syrup disease, where a number of the acids are excreted in the urine, which smells of maple syrup. There are similar disorders of breakdown of carbohydrates, urea and the storage of glucose, all of which are dependent upon early diagnosis and prompt dietary manipulation.
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