Measurement of the skin urocanic acid content in normal and histidinemic infants.

The urocanic acid content of the skin was measured photometrically in a large number of normal and histidinemic infants. A very high content was demonstrated in the normal newborn infants, followed by a rapid decrease throughout early infancy. In contrast, 36 measurements in 17 infants with histidinemia revealed a much lower content even in their newborn periods. Thus, the quantification of skin urocanic acid was considered to be simple and useful for confirming the diagnosis of histidinemia, especially in a neonatal mass-screening program.