Lactate dehydrogenase-immunoglobulin G complex in the serum of the postburn patient.

Lactate dehydrogenase (LDH)-immunoglobulin (Ig) complex has been reported in various diseases (1). Here we describe circulating LDH-IgG complex in a postburn patient; the complex appeared to be related to the progression of burn in this case. A 13-year-old Chinese male was admitted to our hospital with burns over 20% of his body. Some of the relevant laboratory test results and reference intervals (in parentheses) for serum analysis were as follows: alanine aminotransferase, 44 U/L (4–50 U/L); aspartate aminotransferase, 62 U/L (5–45 U/L); g-glutamyltransferase, 17 U/L (4–50 U/L); and alkaline phosphatase, 110 U/L (32–140 U/L). LDH analysis showed high LDH activity (407 U/L; reference interval, 110–240 U/L), and LDH isoenzyme analysis showed abnormal values for the five isoenzymes (LDH-1, 11.8%; LDH-2, 15.8%; LDH-3, 17.6%; LDH-4, 42.5%; and LDH-5, 5.4%) and an extra band, LDH-6 (6.8%; Fig. 1A) LDH activity was measured by a spectrophotometric assay with a CX-7 automatic biochemistry analyzer (Beckman). The assay conditions were largely based on the method described by Wroblewski and LaDue (2). LDH isoenzymes in serum were electrophoretically fractionated with the Paragon electrophoretic system. Bands containing activity were made visible by use of d,l-lactate and NAD as the substrate, phenazine methosulfate as the intermediate, and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide as the final hydrogen acceptor. Isoenzyme bands were scanned with the Appraise densitometer system (Beckman). A broad band in the LDH-4 isoenzyme region characterized the patient’s LDH isoenzyme pattern, with the apparent appearance of an extra band, LDH-6 (Fig. 1). The patient’s erythrocyte LDH isoenzyme patterns were normal; therefore, it was not a genetic mutation that caused this anomaly, because a genetic mutation changes erythrocyte and serum LDH isoenzyme patterns (3). The presence of LDH-IgG complex in the patient’s serum was demonstrated by counter immunoelectrophoresis (Fig. 1B) (4). With his symptoms improved, the patient’s serum LDH activity and isoenzymes gradually returned to reference values. One month after admission, his serum LDH concentration was normalized to 165 U/L, and his LDH isoenzymes were almost within health-related values (LDH-1, 20.8%; LDH-2, 28%; LDH-3, 27%; LDH-4, 19.1%; and LDH-5, 4.2%). Other laboratory test data were as follows: alanine aminotransferase, 26 U/L; aspartate aminotransferase, 34 U/L; g-glutamyltransferase, 18 U/L; and alkaline phosphatase, 83 U/L. The LDH-Ig complex might be associated with the pathophysiology of this case. There have been many reports on abnormal isoenzyme patters of plasma LDH in various diseases (5–7). However, in China there are few reports on LDH-Ig complexes. To our knowledge, ours is the first case of LDH-Ig complex in the serum of postburn patients. The exact mechanism of the formation of LDH-Ig complex under disease conditions must be elucidated.