Serum and faecal lysozyme in inflammatory bowel disease.

Lysozyme (EC 3.2.1.17) concentrations were measured in the serum and stools of patients with inflammatory bowel disease and compared with the concentrations in similar material from normal controls, patints with non-inflammatory gastrointestinal disease, and patients without gastrointestinal disease. By the turbidometric method, values of lysozyme (microgram/ml +/- SD) are considerably greater in the serum of patients with active Crohn's disease (9.2 +/- 2.7) than in the serum of healthy controls (4.4 +/- 2.0). They do not, however, distinguish individual patients with Crohn's disease from those with ulcerative colitis nor from those with a variety of other gastrointestinal conditions. The lysoplate method gives much higher values for serum lysozyme than the turbidometric method but there is a considerable overlap between the results for patients with Crohn's disease (60.1 +/- 30.7) and normal controls (27.4 +/- 17.5). There is only a moderate correlation between the results given by the two methods (r = 0.56) and it is suggested that factors other than enzyme activity and methodological variation are responsible for the observed differences. This is supported by the finding that, with Crohn's disease in remission, serum lysozyme values (lysoplate) return to normal values but with the turbidometric method remain raised. Mean faecal lysozyme levels, expressed either as a concentration or as total daily excretion, in patients with inflammatory bowel disease are very significantly greater than values in healthy controls and in diseased subjects without diarrhoea but are not significantly different from those subjects with other causes of diarrhoea.