Overlaps between AA, PNH, and MDS. Although conceptually representing discrete disease entities, AA, PNH, and MDS frequently coexist or show mutual transitions within a same patient, apart from the ambiguity in actual diagnosis due to the lack of conclusive evidence or misdiagnosis because of resembling clinical presentations. Immune-mediated BM destruction can occur at the same time of emergence of PNH or evolution of malignant clones, causing a diagnostic overlap between these different disease concepts. Increased ring sideroblasts (RS) are rarely seen in AA. ICUS, idiopathic cytopenia of undetermined significance.