A disorder characterized by excessive numbers of mast cells and tissue infiltration by these cells is systemic mastocytosis. In this condition, mutations of c-kit (Asp 816 Val mutation) occur (11,116-118), and a subsequent pathological infiltration of affected tissue by mast cells may be seen, resulting in many of the manifestations (119). The patients may present with skin lesions (pigmented macules that urticate with contact [Darrier's sign]) or systemic symptoms arising from mast cell infiltration of solid organs, such as the liver, spleen, lymph nodes, and bone marrow (119,120). Cutaneous manifestations include urticaria pigmentosa, diffuse and erythematous mastocytosis, mastocytoma (mast cell deposits or tumors), and telangiectasia macularis eruptiva perstans (121). Some patients have skin limited and indolent, slowly progressive disease, whereas others develop rapidly progressive and fatal mast cell leukemia, a feature especially found in some patients with the c-kit mutation (13,122, 123). Osteoporosis is often a feature of mastocytosis, and mast cells may contribute to bone resorption (124). Patients with mastocytosis may develop myelo-proliferative syndromes, myelodysplasia, and/or lymphoreticular malignancy, the mechanisms of which are unknown (125). Interestingly, the marker, a-tryptase is elevated in the serum of patients and provides us with an excellent diagnostic clinical tool (126). By inducing angiogenesis, the secretion of VEGF and bFGF, and the elaboration of collagenases, mast cells can contribute to tumor pathology and invasiveness (127-129).
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