It has been suggested that myeloid neoplasms with isolated isochromosome 17q[MN i(17q)] comprise a distinct entity with poor prognosis. However, literature reports show a considerable clinical and molecular heterogeneity. We describe a 58-year-old male patient who was diagnosed as refractory anemia with multilineage dysplasia and ringed sideroblasts with isolated i(17q). Though he initially responded well to erythropoietin, he gradually progressed to an aggressive form of MDS/MPN refractory to azacytidine and died 29 months after first diagnosis. Notably, in contrast to disease advancement, his karyotype reverted to normal, whereas his mutational profile remained unchanged. To our knowledge this is the first report of karyotype normalization during disease progression in patients with MN i(17q), suggesting that the i(17q) anomaly is dispensable for the leukemic transformation and highlighting the underlying clinical and molecular complexity which both have to be resolved before the establishment of MN with isolated i(17q) as a distinct entity.