In which condition would serum lactate dehydrogenase be highest?

Serum lactate dehydrogenase (LDH) levels can signify tissue damage and are often elevated in various conditions. In the context of pernicious anemia, LDH is typically elevated due to hemolysis of red blood cells associated with this condition. Pernicious anemia results in a deficiency of vitamin B12, leading to ineffective erythropoiesis and subsequent hemolysis, which can release LDH into the bloodstream.

While other conditions listed, such as myocardial infarction, acute hepatitis, and muscular dystrophy, can also cause elevations in LDH, they usually lead to an elevation of specific LDH isoenzymes rather than a significant overall increase in serum LDH levels. For instance, LDH may be markedly elevated in acute hepatitis related to the level of liver damage, and myocardial infarction can increase LDH due to myocardial tissue injury. However, pernicious anemia often presents with very high levels of LDH related to the extensive hemolysis and subsequent release from damaged cells.

Thus, in cases of pernicious anemia, the presence of a high level of serum LDH is a strong indicator of the condition's associated hemolysis.