Coexistence of Chronic Myelomonocytic Leukemia and Ulcerative Colitis With Rapid Progression to Acute Myelomonocytic Leukemia: A Case Report.

Chronic myelomonocytic leukemia (CMML) is a clonal myeloid neoplasm characterized by sustained peripheral blood monocytosis and variable dyspoiesis. We present a case of a 64-year-old male who presented with severe non-bloody diarrhea, peripheral blood neutrophilia, and monocytosis. He was diagnosed with myeloproliferative CMML type 0 and ulcerative colitis (UC). Next-generation DNA sequencing of a bone marrow sample demonstrated mutations of the TET2, ASXL1, NRAS, and SRSF2 genes along with low-level JAK2^V617F mutation. Both TET2 and SRSF2 mutations are associated with systemic inflammatory and autoimmune disease (SIAD), which includes UC. The patient's UC was managed successfully with vedolizumab infusions. The patient's concurrent CMML was monitored with a "wait and watch" approach. After five months, the patient asymptomatically tested positive for coronavirus disease 2019 (COVID-19). Seven months after his diagnosis of CMML, the patient presented in severe respiratory distress with acute left upper quadrant pain, splenomegaly, and multiorgan failure. A peripheral blood smear demonstrated marked leukocytosis (283 x 10^9 /L) with 39% blasts/promonocytes without Auer rods. The patient was diagnosed with acute myeloid leukemia with myelomonocytic features (AMML). In this report, we discuss the diagnosis of combined CMML and SIAD, mechanisms of immunoregulatory dysfunction that have been suggested to result in CMML progression, and the clinicopathologic significance of the patient's molecular abnormalities.