An unusual response to 5‐azacitidine by a patient with chronic myelomonocytic leukemia

KEY CLINICAL MESSAGE: Hypomethylating agents may be useful in some but not all cases of myelodysplastic syndromes. In some versions of these conditions, this treatment may yield deleterious results. ABSTRACT: Chronic myelomonocytic leukemia (CMML) is considered to be a heterogeneous group of hematopoietic neoplasms. Usually it shares the features of myeloproliferative neoplasms (MPN) and myelodysplastic syndromes (MDS) and is known as MDS/MPN. It occurs mostly in the elderly and has an inherent tendency to transform to acute myeloid leukemia. FDA has approved hypomethylating agents (HMAs) such as 5‐azacitidine (AZA) and decitabine (DEC) for the treatment of this disorder. The extent of response rate to AZA varies considerably among patients. Our report describes a patient with CMML who not only did not respond to a conventional dose of intravenous (IV) therapy with AZA, but showed marked progression of the disease with the leucocyte count rising exponentially while undergoing the aforesaid treatment. We believe this is the first such case reported in the currently extant literature.