Systemic lupus erythematosus and infection: a controlled and prospective study including an epidemiological group.

An epidemiological group of 60 SLE patients was studied; 162 infections were observed prospectively for an aggregate of 1366 months. Bacterial infection was more frequent in the SLE patients than in matched controls but only slightly more frequent than in matched rheumatoid arthritis patients. The rheumatoid arthritis patients, also matched with regard to corticosteroid dosage, showed a tendency towards an increased infection rate only. Lower urinary tract infections were comparable in all three matched groups. In a total of 102 SLE patients studied, including the epidemiological group, clinical SLE activity was accompanied by an increase in the frequency of bacterial infection. In 49 patients bacterial infections were more common after flare than before. There was a high incidence of mucocutaneous infections induced by S. aureus, where skin traumatisation was an added risk factor. No increase of opportunistic infections was found in matched groups, but 26 such infections occurred in the subjects as a whole, and they were seen to be more frequent in conjunction with steroid-treated active SLE. Admission to hospital because of suspected infection was common, and infection was the cause or a contributory factor in five of the seven deaths among SLE patients.