Serum lysozyme in Crohn's disease and ulcerative colitis.

Serum lysozyme (muramidase) concentrations were determined in patients with different types of inflammatory bowel disease and in normal subjects. The mean (plus or minus S.E.M.) lysozyme concentration for each group was as follows: controls, 8.8 plus or minus 0.3, ulcerative colitis, 9.3 plus or minus 0.6, Crohn's disease, 26.3 plus or minus 1.4. a and bacterial and nonbacterial enteritis, 8.9 plus or minus 0.7 mug per milliliter. Thus, mean enzyme levels were significantly greater in Crohn's disease than in ulcerative colitis (p smaller than 0.001), bacterial and nonbacterial enteritis (p smaller than 0.001) and healthy volunteers (p smaller than 0.001). The elevation of serum lysozyme in Crohn's disease may be related to tissue macrophages because no correlation was found between either the serum lysozyme concentration and the white-cell counts or the absolute numbers of circulating granulocytes or monocytes. Our findings suggest that serum lysozyme may be useful in the differential diagnosis of Crohn's disease from other types of bowel inflammation.