A 67-year-old woman was diagnosed in 2009 with refractory anemia with excess blasts-1 after being referred for mild anemia and neutropenia without hemolysis or abnormal erythrocyte morphology. Marrow karyotype was normal. She was not treated for 6 years, but had regular checks of her complete blood count (CBC), showing fluctuating thrombocytosis, and bone marrow (BM) aspiration yearly. She remained stable and in good general condition until December 2015, when she complained of fatigue.Her CBC showed mild normocytic hypochromic anemia (hemoglobin, 9.2 g/dL) and no neutropenia, but marked thrombocytosis. Molecular analyses showed no mutation of JAK2, CALR, or MPL. The blood smear disclosed new significant elliptocytosis (panel A), and laboratory studies found undetectable haptoglobin. BM aspiration showed 10.5% blast cells (ie, refractory anemia with excess blasts-2). The neutrophils appeared hypogranulated and hypolobulated and frequently displayed erythrophagocytosis (panel B, arrows). Karyotypic examination disclosed a del(20q). More interestingly, the deleted chromosomal section contained the gene encoding erythrocyte membrane protein band 4.1-like 1 in region 20q11.2-q12 (karyotype 46,XX,del(20)(q11q13)[20]). This new chromosomal anomaly may be responsible for the development of elliptocytosis.