A clonal (malignant) hematopoietic disorder with an acute onset, affecting the bone marrow and the peripheral blood. The malignant cells show minimal differentiation and are called blasts, either myeloid blasts (myeloblasts) or lymphoid blasts (lymphoblasts). The disease is acute leukemia (Monarch Disease Ontology id MONDO_0010643). Also known as: acute leukaemia (disease), acute leukemia (disease).