Erythrocyte Sensitivity to In‐Vitro Lysis in Leukaemia

S ummary . In‐vitro lysis tests with cold antibody, sucrose and acidified serum have been carried out on 139 patients suffering from leukaemia, lymphomas and other bone‐marrow malignancies. None of the patients tested showed a positive acidified‐serum test but a positive cold‐antibody lysis occurred in a significant number of patients with acute leukaemias, especially the myeloid type in whom 58% were positive with varying degrees of lysis. In some patients the positive test persisted for a long time even when the patient was in haematological remission, suggesting the possibility that the defective red cells were derived from a persistently abnormal clone. Minor degrees (less than 5%) of lysis occurred with the sucrose‐lysis test in 40% of patients with chronic granulocytic leukaemia and more than 5% lysis occurred in one patient with erythroleukaemia. Anaemia was twice as common in patients with a positive cold‐antibody lysis than in patients with no lysis. In the cases of malignant lymphomas there appeared to be a relationship between positive cold‐antibody lysis and bone‐marrow infiltration. The results obtained do not add definitive evidence to the hypothesis that PNH is related to the myeloproliferative disorders but they do demonstrate that in the conditions which were studied, notably acute myeloid leukaemia, there is dyserythropoiesis and the production of an abnormal erythrocyte with membrane defect; this may suggest that the affected red cells are derived from an abnormal stem cell common to both granulopoesis and erythropoiesis.