Inborn errors of metabolism (IEM) individually are rare but collectively are common. In IEMs single gene defects are responsible for the abnormalities in the synthesis or catabolism of proteins, carbohydrates or fats by way of defective enzymes or transport proteins, resulting in a block of metabolic pathway. The male to female ratio is 1:1 for X-linked dominant if transmission is from mother to child (1). Effects are due to toxic accumulations of the substrates before block, intermediates from alternative metabolic pathways, defects in energy production and use caused by a deficiency of products beyond the block or a combination of these metabolic deviations. Figure I shows the theoretical consequences of metabolic disorders. Nearly every metabolic disease has several forms that vary in age of onset, clinical severity and often mode of inheritance. Proper history from parents has a role in suspecting IEM. Parental consanguinity increases the chance of autosomal recessive IEM (2).