Levels of mast-cell growth factors in plasma and in suction skin blister fluid in adults with mastocytosis: Correlation with dermal mast-cell numbers and mast-cell tryptase

Background: Mast-cell accumulation has been observed in the skin and other organs of patients with systemic indolent mastocytosis (SM). The basis for this pathologic increase is not fully understood. Objective: We sought to determine levels of mast-cell growth factors in the skin and plasma of patients with SM, patients with atopic dermatitis (AD), and healthy individuals and to correlate these levels to dermal mast-cell numbers and levels of mast-cell tryptase. Methods: Skin suction blister fluid and plasma levels of stem-cell factor, IL-3, IL-4, IL-6, vascular endothelial growth factor, and total mast-cell tryptase were analyzed by means of ELISA. The number of mast cells was determined in a biopsy section taken from adjacent skin. Results: Mast-cell numbers in the dermis were higher in patients with SM compared with numbers in patients with AD (P <.001) or in healthy control subjects (P <.0001) and correlated with tryptase levels in both skin blister fluid (P <.0001) and plasma (P <.0001). Stem-cell factor and vascular endothelial growth factor levels in the skin blister fluid and plasma of patients with SM were not significantly different from those in patients with AD or healthy control subjects. IL-3 and IL-4 levels were below the limit of detection. IL-6 levels were significantly increased in the plasma of patients with SM compared with in plasma of patients with AD (P <.002) and healthy control subjects (P <.0001) and correlated with plasma tryptase levels (P <.05) and dermal mast-cell numbers (P <.02). Conclusion: Because elevated levels of IL-6 could contribute to the fever, fatigue, and osteoporosis observed in patients with SM and because IL-6 is antiapoptotic for mast cells, IL-6 could potentiate the biologic consequences of this disease.