A possible mechanism of mast cell proliferation in mastocytosis.

The abnormality in mastocytosis is the excessive accumulation of mast cells in the affected tissue. The growth and differentiation of human mast cells are quite dependent on stem cell factor (SCF), the ligand for the protein products of c-kit. Recent studies have demonstrated that all adult patients examined so far carry c-kit point mutations, leading to SCF-independent autophosphorylation of the receptor and autonomous cell growth. On the other hand, typical pediatric patients have been found to bear no activating Asp816Val mutation in c-kit. Although most mastocytosis patients are children, the mechanism by which mast cells proliferate in these pediatric patients remains unclear. Recently, were reported that human mast cells obtained from adult skin could dramatically proliferate when cultured with SCF. From these experimental results, it is speculated that local excessive production of SCF results in the mast cell proliferation in pediatric patients.