Two further cases clinically diagnosed as CDA‐I (P44 and P54) were found to have mutations in non‐CDA genes (RPS19 as discussed above) and PKLR. The latter (P54) was an 18‐month‐old transfusion‐dependent girl in whom bone marrow analysis showed erythroid hyperplasia with significant dyserythropoiesis and ~30% of erythroblasts were reported as exhibiting ‘Swiss‐cheese heterochromatin’, leading to a clinical diagnosis of CDA and pyruvate kinase (PK) levels were therefore not tested. The gene discussed is PKLR; the disease is congenital dyserythropoietic anemia.