Soluble stem cell factor receptor (CD117) and IL-2 receptor alpha chain (CD25) levels in the plasma of patients with mastocytosis: relationships to disease severity and bone marrow pathology

Systemic mastocytosis is a disease of mast cell proliferation that may be a ssociated with hematologic disorders, There are no features on examination that allow the diagnosis of systemic disease, and mast cell-derived mediato rs, which may be elevated in urine or blood, may also be elevated in indivi duals with severe allergic disorders. Thus, the diagnosis usually depends o n results of bone marrow biopsy. To facilitate evaluation, surrogate marker s of the extent and severity of the disease are needed. Because of the asso ciation of mastocytosis with hematologic disease, plasma levels were measur ed for soluble KIT (sKIT) and soluble interleukin-2 receptor alpha chain (s CD25), which are known to be cleaved in part from the mast cell surface and are elevated in some hematologic malignancies, Results revealed that level s of both soluble receptors are increased in systemic mastocytosis. Median plasma sKIT concentrations as expressed by AU/mL (1 AU =1.4 ng/ mt) were as follows: controls, 176 (n = 60); urticaria pigmentosa without systemic inv olvement, 194 (n = 8); systemic indolent mastocytosis, 511 (n = 30); system ic mastocytosis with an associated hematologic disorder, 1320 (n = 7); aggr essive mastocytosis, 3390 (n = 3), Plasma sCD25 levels were elevated in sys temic mastocytosis; the highest revels were associated with extensive bone marrow involvement. Levels of sKIT correlated with total tryptase levels, s CD25 levels, and bone marrow pathology These results demonstrate that sKIT and sCD25 are useful surrogate markers of disease severity in patients with mastocytosis and should aid in diagnosis, in the selection of those needin g a bone marrow biopsy, and in the documentation of disease progression. (B lood. 2000;96: 1267-1273) (C) 2000 by The American Society of Hematology.