<unk>  is characterized by increased levels of histidine, histamine and imidazole in blood, urine and cerebrospinal fluid. This also results in decreased levels of the metabolite urocanic acid in blood, urine, and skin cells. In Japan, neonatal screening was previously performed on infants within 1 month of birth; infants demonstrating a blood histidine level of 6 mg/dl or more underwent careful testing as suspected<unk>  cases. A typical characteristic of<unk>  is an increase in the blood histidine levels from normal levels (70-120 μM) to an elevated level (290-1420 μM). Further testing includes: observing histidine as well as imidazolepyruvic acid metabolites in the urine. However, neonatal urine testing has been discontinued in most places, with the exception of Quebec.
Histidinemia
Isovaleric acidemia
Pipecolic acidemia
Galactosemia
Hyperphenylalaninemia
D-Glyceric acidemia
Hypoplasminogenemia
Hawkinsinuria