Histamine metabolism in polycythaemia vera.

Histamine metabolism was studied in 35 patients with polycythaemia vera (PV) at different stages of their disease and compared with controls and patients with secondary polycythaemia. In addition to blood and urinary histamine the main urinary metabolites of histamine, methylhistamine (MeHi) and 1-methyl-4-imidazoleacetic acid (MeImAA) were measured. In patients with active PV the excretion of MeHi and MeImAA was significantly higher than in controls and secondary polycythaemia, indicating an increased histamine formation. The MeImAA excretion was correlated to the blood histamine level, the degree of blood basophilia, the total white blood count and the spleen volume. The blood histamine level was significantly higher in PV patients compared with controls and secondary polycythaemia. No patients with secondary polycythaemia had an increased blood histamine level. With the bio-assay technique used in this study the urinary excretion of histamine in the PV patients was within the normal range. There was no correlation between the increased histamine formation and "histamine-related symptoms". Pruritus and duodenal ulcer occurred with a similar frequency in patients with and without increased MeImAA excretion. The similarity between the disturbance of the histamine metabolism in PV and that found by other authors in chronic myeloid leukaemia is pointed out.