Monocytic crisis of chronic myeloid leukemia in the era of tyrosine kinase inhibitor.

A 47-year-old man was diagnosed with Philadelphia chromosome-positive chronic myeloid leukemia (CML) in October 2005. He could not receive treatment with imatinib mesylate due to his economic circumstances. He was consequently treated with hydroxyurea with partial hematological remission until June 2008. Although imatinib mesylate was started thereafter, the adherence to this treatment was poor because of his occupational circumstances. In September 2009, imatinib mesylate was switched to nilotinib, with a subsequent phase of acceleration of the disease, presumably due to his poor adherence to the treatment. Dasatinib was started in September 2010, with transient hematological response and final blastic crisis of the disease in January 2011, regardless of improved adherence. Blast cells showed immature monocytic morphology and were positive for α-naphtylbutyrate esterase staining. They also expressed surface CD14 and CD64 antigens. A diagnosis of rare monocytic crisis of CML was made. He was treated with low-dose nilotinib following cytoreduction with MEC (mitoxantrone, etoposide, and cytarabine) chemotherapy. Severe leucopenia without circulating leukemic cells continued for about 2 months with sustained hepatosplenomegaly, and he died of pneumonia in March 2012. Necropsy showed severe bone marrow hypoplasia with focal infiltration of mature leukemic cells and similar infiltration in the liver.