IL-6 levels in peripheral blood have been correlated with severity of disease not only in systemic mastocytosis but also in acute and chronic urticaria as well as asthma.4, 5, 6, 7, 8 Increased IL-6 levels in mastocytosis are correlated with BM pathology, hepatosplenomegaly, osteoporosis, levels of tryptase,4 and risk of systemic disease progression.7 This evidence concerns the gene IL6 and systemic mastocytosis.