Lactate dehydrogenase isoenzyme patterns in blood cells from histiocytosis X children.

To find a clinical assay for histiocytosis X (HX) diagnosis, measurements were made of both activity and isoenzyme distribution of lactate dehydrogenase (LDH; EC 1.1.1.27) from the blood cells of 6 acute phase and 9 remission patients. A significant increase in the LDH activity measured in the monocytes and lymphocytes isolated from the blood of the acute phase patients was found. The increased activity was due to an enhancement of the normal pattern of LDH isoenzymes in these cells and not to a change in isoenzyme distribution. No increase was found in monocyte LDH isoenzymes from the patients in remission.