Subclinical microbial infection in patients with chronic plaque psoriasis.

Epidemiological evidence implicates bacterial infection as a common triggering stimulus for psoriasis. Recent studies suggest that continuing, subclinical streptococcal and staphylococcal infections might be responsible not only for relapse of acute guttate psoriasis but also for a new episode of chronic plaque psoriasis. In this study 195 patients suffering from a severe form of chronic plaque psoriasis hospitalized between 1996 and 1998 were examined. The presence of subclinical microbial infection of the upper respiratory tract was studied by the cultivation of pathogens from this area. Patients with other provoking factors, such as a positive history of taking any drugs that may exacerbate psoriasis, endocrine and metabolic factors, alcohol abuse, trauma, dental focus and clinically evident bacterial infection, were excluded. Subclinical streptococcal and/or staphylococcal infections were detected in 68% of tested patients and in only 11% of the control group. The results of this study indicate that subclinical bacterial infections of the upper respiratory tract may be an important factor in provoking a new relapse of chronic plaque psoriasis. Searching for, and eliminating, microbial infections could be of importance in the treatment of psoriasis.