Hydantoin-5-propionic aciduria in folic acid nondependent formiminoglutamic aciduria observed in two siblings

Hydantion-5-propionic acid was detected in massive amounts in the urine of two previously described sisters with folic acid nondependent formiminoglutamic aciduria. HPA was identified rigorously, e.g. by gas chromatography-mass spectrometry, and was measured quantitatively by selected ion monitoring (mass fragmentography) using deuterated HPA as internal standard. Before histidine loading, both girls with the postulated formiminotransferase deficiency excreted an amount of HPA more than 50 times greater than the control subjects. After histidine ingestion, HPA excretion was still doubled or tripled. With the exception of the father, the values for the other members of the family also markedly exceeded the normal range and were of the same order of magnitude as in folate deficiency. Measurement of HPA excretion in urine seems to be a valuable supplement or alternative to the enzymatic FIGu test for the detection of general or functional folate deficiency or impaired folate utilization and it will be indispensable for the detection of (as yet unknown) 4-imidazolone-5-propionic acid hydrolase deficiency.