Increased serum lactate dehydrogenase isoenzyme 1 and macro creatine kinase type 2 in a patient with lung cancer

A 72-yr-old man, having a lung tumor with metastatic spread to liver and bone, was hospitalized with a lactate dehydrogenase (LD; EC 1.1.1.27) activity and a creatine kinase (CK; EC 2.7.3.2) activity in serum of 30 and 2 times the upper reference limit (URL), respectively. The LD isoenzyme-1/LD activity ratio was 62% (2 times URL). This ratio was maintained throughout hospitalization, during which LD activity increased up to 90 times URL. Macro CK type 2 activity represented almost all of the CK activity, which increased up to 4 times URL during hospitalization. The patient died the 29th day after admission. The enzyme abnormalities were thought to stem from tumor tissue.