medwireNews: A 13-year cohort study indicates that systemic rheumatic diseases are associated with an increased incidence of opportunistic infections, and suggests that patients with polymyositis or dermatomyositis (PM/DM) have the highest rates.
In light of their findings, Chun-Yu Lin (National Cheng Kung University, Tainan City, Taiwan) and study co-authors suggest: “Careful observation and preventative therapy for opportunistic infections may be warranted in selected PM/DM patients, especially during the first year after diagnosis.”
Using national health insurance data, Lin and team identified 76,966 individuals who had one of five rheumatic diseases – PM/DM, systemic lupus erythematosus (SLE), systemic sclerosis (SSc), rheumatoid arthritis (RA), or primary Sjögren’s syndrome (pSS).
The researchers investigated the occurrence of nine different opportunistic infections in the patients. These were aspergillosis, candidiasis, Cryptococcus, Pneumocystis jirovecii pneumonia, cytomegalovirus, salmonellosis, herpes zoster, tuberculosis, and non-tuberculosis mycobacterium. Toxoplasmosis, coccidioidomycosis, and histoplasmosis infections were also investigated, but were omitted from analyses because fewer than two events were detected.
The highest incidence rate of opportunistic infections, of 61.3 cases per 1000 person–years, was observed among the 2270 patients with PM/DM. This was significantly higher than the next highest rate of 43.1 cases per 1000 person–years seen in the 15,961 patients with SLE, the team reports in Arthritis Research & Therapy.
And this was followed by rates of 31.6, 25.0, and 24.1 cases per 1000 person–years for patients with SSc (n=2071), RA (n=38355), and pSS (n=18309), respectively.
Lin and colleagues describe their study as “the first to demonstrate that the risks of [opportunistic infection] vary for each specific disease, with the highest risk observed for PM/DM.”
The authors propose that PM/DM patients might have a heightened risk for opportunistic infections due to an increased vulnerability to pulmonary infections as a result of interstitial lung disease and, compared with SLE patients, a more frequent need for intensive immunosuppression.
Of the nine opportunistic infections studied, the researchers found that herpes zoster, candidiasis, and tuberculosis were the most common, and that the risk for all opportunistic infections was highest in the first year after diagnosis of a rheumatic disease. In the case of PM/DM, for example, the risk for developing an opportunistic infection was about 5.4 times greater in the first year than at 5 or more years after diagnosis.
Lin and study co-authors point out that their dataset lacked information pertaining to the activity or severity of the rheumatic disease, and also did not account for glucocorticoids or immunosuppressant treatment.
Despite these limitations, the researchers reinforce “the importance of monitoring for [opportunistic infection] development during the treatment of these autoimmune rheumatic diseases, especially for patients with PM/DM.”
By Hannah Kitt
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Arthritis Res Ther 2019; 21: 211