Muramidase (lysozyme) in Crohn's disease and in ulcerative colitis

Estimation of lysozyme (LZM) activity in the serum was suggested as a valuable test to distinguish between Crohn's disease and ulcerative colitis. Subsequently several reports either supported or denied the original observation. Selection of patients and methodological differences were suggested as an explanation for the controversy. We estimated serum LZM in a large group of patients using the lysoplate method and human LZM as a standard. The conditions of the assay were strictly standardized. In 90 patients with Crohn's disease the LZM level was 8.3 +/- 2.1 (SD) microgram/ml, in 57 patients with ulcerative colitis was 7.4 +/- 2.0 (SD) microgram/ml, and in 40 healthy individuals it was 7.0 +/- 1.2 (SD) microgram/ml. Although the difference between the mean LZM levels in Crohn's disease and in ulcerative colitis was statistically significant, there was a definite overlapping of values between these two diseases. No significant correlation of LZM level to the duration or extent of the disease, activity, or treatment was found in Crohn's disease. In ulcerative colitis the LZM level was often a little higher in severe disease, especially when the whole colon was involved.