<prompt> An infant presents with history of seizures skin rashes. Investigations show metabolic acidosis increased blood ketone levels and normal NH3. This child is likely to be suffering fromPropionic acidurariaUrea cyclic disorderPhenylketonuriaMultiple carboxylase deficiency  <response>: In the degradation of valine, leucine, isoleucine essential, branched chain aminoacids, the intermediate metabolites are all organic acids, and deficiency of any of the degradative enzymes except for transminases causes acidosis due .to accumulation of organic acids before the enzymatic block. Although most clinical manifestation are non specific, some, manifestations may provide important clues to the nature of enzyme deficiency. I have below, outlined, an approach to infants with a typical presentation, suspected of having an organic acidemia. 