Multiple skin lesions caused by imatinib mesylate treatment of chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is a myelopro‐ liferative disorder, caused by the clonal malig‐ nant transformation of a single pluripotent stem cell.1 It results in excessive proliferation of my‐ eloid cells in all stages of maturation in the bone marrow (FIGURE 1A), leukocytosis with a “left shift” in the peripheral blood, and often splenomegaly. CML is a rare disease constituting from 15% to 20% of all newly diagnosed adult leukemias with an average incidence of 1 to 2 cases/100,000 peo‐ ple. The underlying molecular abnormality of CML is the reciprocal translocation t(9;22)(q34;q11), widely known as the Philadelphia chromosome, which produces the chimeric bcr‐abl oncogene that encodes a constitutively activated tyrosine kinase.1,2 CLINICAL IMAGE