Evidence for Delayed Histidine Transamination in Neonates with Histidinemia

Abstract

The excretion of metabolites of histidine transamination by histidinemics, specifically imidazolepyruvic acid (IPA), imidazolelactic acid (ILA), and imidazoleacetic acid (IAA) is less in the neonatal and early infancy periods than in later life; whereas, histidine excretion is generally greater in the early months of life. This suggests that early in life the maturation of histidine transaminase may be delayed.

In screening for histidinemia it is important to recognize that in neonates with histidinemia, IPA excretion may be very low or absent and thus that the ferric chloride test may be negative. For this reason screening procedures that detect increased histidine in urine are much more effective in the early diagnosis of histidinemia than are those procedures that detect only increased histidine metabolite excretion.