Lactate dehydrogenase isoenzyme activity in malignant haematological diseases.

The isoenzymes 1 and 2 (LDH1 and LDH2) of lactic dehydrogenase (LDH) were studied in the serum of 32 patients with malignant haematological diseases. In non-Hodgkin lymphoma (NHL) a diminution in LDH1 and an increase in LDH2 was a sign of evolution towards a more aggressive phase of the disease, or the absence of clinical remission, even when no significant variation of total LDH can be observed in the serum. In acute lymphoblastic leukaemia (ALL), the isoenzymatic variations are not an early indication of relapse. No significant variations in serum LDH or of these isoenzymes was observed in chronic lymphocytic leukaemia (CLL) or Hodgkin's disease (HD). Only in NHL did the variations of LDH1 and LDH2 appear to be a biochemical marker of the tumour process and of cellular differentiation.