Serum lysozyme concentration in silicosis patients and workers exposed to silica dust.

Lysozyme in serum (LZM, EC 3.2.1.17) was assayed in 135 male patients with silicosis. Twenty-eight of the patients had controls matched for exposure to silica dust, age and sex but with no radiographical signs of silicosis. A reference group without exposure to silica dust was composed of 34 lumberjacks. The mean concentration of serum LZM was higher in silicosis patients (7.8 +/- 2.8 mg/l, n = 28) than in the controls exposed to silica (6.0 +/- 1.7 mg/l, p less than 0.05), or in the lumberjacks (5.7 +/- 2.1 mg/l, p less than 0.01). There was an association between serum LZM concentration and radiographic severity of silicosis, and on a group basis an association of serum LZM concentration with the progression of silicosis. In the multivariate regression analysis the highest regression coefficients were found for progression of small opacities as well as patient age. The results suggest that the elevation of LZM concentration is associated with the progression of the disease.