Elevations of LD isoenzymes LD4 and LD5 on electrophoresis are most often associated with which condition?

• A. Liver disease
• B. Hemolytic anemia
• C. Myocardial infarction
• D. Pulmonary edema

Answer: (A)

The key idea is that LDH has tissue-specific isoenzymes, and the pattern on electrophoresis reflects where the enzyme is coming from. LD4 and LD5 are the isoenzymes most abundant in liver tissue (and to some extent in skeletal muscle). When the liver is damaged, hepatocytes release LDH, especially the LD4 and LD5 forms, into the bloodstream. That release shifts the electrophoresis pattern toward LD4 and LD5, making this pattern most characteristic of liver disease.

In contrast, myocardial infarction tends to elevate LDH isoenzymes that reflect heart tissue, mainly LDH-1 and LDH-2, rather than LD4 and LD5. Hemolytic anemia can raise overall LDH due to red cell breakdown but without a specific predominance of LD4/LD5. Pulmonary edema does not have a distinctive LDH isoenzyme signature. So the LD4/LD5 elevation points most consistently to liver disease.