VALUE OF URINARY N-METHYLHISTAMINE MEASUREMENTS IN CHILDHOOD MASTOCYTOSIS

Background: Histamine is an indicator of mast cell activation. N-methy lhistamine (NMH) is a metabolite of histamine that can he measured in urine. Objective: Our purpose was to assess the usefulness of determin ing urinary NMH levels for the diagnosis and follow-up of patients wit h mastocytosis. Methods: Urinary NMH levels were determined in 44 pati ents and were correlated with disease activity and extension. The cont rol group consisted of 24 children without mastocytosis or any other s kin disease. Results: A significant negative correlation was found bet ween NMH and age in patients with active mastocytosis and in the contr ol group. Adjusted for age, NMH values were significantly higher in pa tients with active mastocytosis. There was a significant difference in NMH values between patients with diffuse cutaneous mastocytosis, pati ents with active urticaria pigmentosa, and patients with active mastoc ytomas. However, there was a substantial overlap of NMH values in the different subgroups. Conclusion: Urinary NMH values tend to decrease w ith age. Urinary NMH values correlated with the extent and the activit y of the disease. High NMH values suggest more extensive involvement.