[Hemopyrrollactamuria (HPU); from spots to pseudo-disease].

In recent years, patients in the Netherlands confront their doctors with the diagnosis 'haemopyrollactamuria' (HPU), based on the presence of the haemopyrrollactam complex in their urine. The diagnosis is made by a commercial laboratory in the Netherlands (www.keac.nl). We have not been able to find peer-reviewed scientific literature on this metabolic disease. The haemopyrrollactam complex represents the so-called mauve spot, which was the subject of much controversy in schizophrenia research in the previous century. Reviewing all of the available data, we feel that HPU should be classified as a pseudo-disease.