Clinical findings in HHH syndrome are non-specific. If the disorder is suspected, laboratory testing can provide diagnostic information. Plasma amino acid analysis will show elevated<unk>  levels, and urine amino acids will detect homocitrulline. Orotic acid may also be elevated. Ammonia levels can be variably elevated. If these findings are present, molecular testing may provide additional confirmatory information.
Ornithine translocase deficiency
Holocarboxylase synthetase deficiency
Guanidinoacetate methyltransferase deficiency
Carbamoyl phosphate synthetase I deficiency
Malonyl-CoA decarboxylase deficiency
Aminoacylase 1 deficiency
Arginine:glycine amidinotransferase deficiency
Adenylosuccinate lyase deficiency