Lactate Dehydrogenase Isoenzymes in Alveolar Proteinosis

To the Editor:—  Pulmonary alveolar proteinosis is a disease of unknown etiology, the active phase of which is marked by an increase in total serum lactate dehydrogenase ( LDH) level.^1-3 Despite the many reports which document the increased total LDH level in the serum and despite an extensive review of the English literature on the subject, I have been unable to find reports of isoenzymes of LDH. Recently, however, in performing a pulmonary lavage on a patient with alveolar proteinosis, we had an opportunity to record the LDH isoenzymes in the lavage effluent as well as in the serum before lavage.

Report of a Case:—  A 61-year-old Negro man was admitted to the West Tennessee Chest Disease Hospital with increasing dyspnea and diffuse pulmonary infiltrates bilaterally. Review of yearly roentgenograms of the chest showed the disease to have started one year prior to admission. Numerous examinations of sputum for mycobacterial,