Pyruvate kinase (PK) activation is emerging as a promising treatment modality for numerous congenital hemolytic anemias of diverse pathophysiology, and one agent, mitapivat, is already licensed to treat patients with congenital PK deficiency. However, PK deficiency may also be acquired in the setting of clonal myeloid disorders and other pathologies, where it may result in severe hemolytic anemia and remains without known therapies. This case report describes the novel application of mitapivat therapy in a patient with acquired PK deficiency causing red cell transfusion dependence, liberating the patient from transfusions and resulting in marked improvement in symptoms and quality of life.