Overall, 46 patients with mastocytosis lacking the D816V KIT mutation and other extracellular membrane/transmembrane KIT mutations who were treated with imatinib and further evaluated for response to therapy have been reported, with an overall response rate of 80% (37/46 cases) [18, 32–35, 37, 42, 45–62]. The gene discussed is KIT; the disease is mastocytosis.