Opportunistic Infection Risk High in Myositis

 Orange colored multiple antibiotic resistant Pseudomonas aeruginosa bacterium. (©ChristophBurgstedt, AdobeStock_296936119)

Among patients with systemic rheumatic diseases, the risk of opportunistic infections was highest in those with polymyositis/dermatomyositis, say researchers writing in Arthritis Research & Therapy this month.

Infection remains a leading cause of hospitalization and death among patients with autoimmune rheumatic disease. The estimated rates of infectious complications ranges from 26 percent to 50 percent among patients with polymyositis/dermatomyositis or systemic lupus erythematosus, with immune abnormalities, and frequent use of corticosteroids and immunosuppressive agents making such patients more susceptible to infections. In addition to common infections, opportunistic infection has emerged as an important complication, but most studies examining opportunistic infections have been single center in design and focused on SLE. Little is known about the rates in other systemic rheumatic diseases.

This cohort study included 2000 to 2013 data from Taiwan's National Health Insurance Research Database to compare the incidence rates of nine opportunistic infections, including candidiasis, aspergillosis, Cryptococcus infection, Pneumocystis jiroveci pneumonia, cytomegalovirus, tuberculosis, and herpes zoster, among 76,966 patients with rheumatoid arthritis, primary Sjogren's syndrome, SLE, polymyositis/dermatomyositis, or systemic sclerosis.

The incidence rate of opportunistic infections was highest for polymyositis/dermatomyositis (61.3/1000 person-years, 95% confidence interval [CI] 56.6–66.2), followed by SLE (43.1/1000 person-years, 95% CI 41.7–44.5), systemic sclerosis (31.6/1000 person-years, 95% CI 28.3–35.1), rheumatoid arthritis (25.0/1000 person-years, 95% CI 24.4–25.7), and primary Sjogren's syndrome (24.1/1000 person-years, 95% CI 23.1–25.2).

“It is important to note that RA patients receiving anti-TNF therapy or other biological agents may experience a higher risk of opportunistic infections, relative to their apparent risk,” wrote the authors, led by Chun-Yu Lin, M.D., of National Cheng Kung University in Taiwan.

Compared to SLE, polymyositis/dermatomyositis was associated with a significantly higher risk of opportunistic infections (hazard ratio 1.18, 95% CI 1.08–1.29). The incidence of opportunistic infections was highest during the first year after diagnosis of the rheumatic disease, diminishing thereafter. The incidence rate of opportunistic infection for patients with polymyositis/dermatomyositis was 5.4 times higher during the first year compared with after five years, which the researchers suggested may be due to the use of lower steroid doses later in disease and higher disease activity soon after onset.

Previous studies that focused on bacterial or opportunistic infections in systemic lupus erythematosus implicated multiple factors, including complement deficiency, low production of interleukin 8, and inadequate chemotaxis and phagocytosis, along with the use of corticosteroids and immunosuppressive agents. One major factor that may have led to substantially higher infection rates among polymyositis/dermatomyositis patients than those with lupus in this study was interstitial lung disease, which has been detected in up to two-thirds of polymyositis/dermatomyositis patients and may increase susceptibility to pulmonary infections with Aspergillus and Mycobacterium pathogens. The authors suggested that the more intensive immunosuppression required in polymyositis/dermatomyositis than in SLE may also explain the difference in the incidence rate of opportunistic infections.

“Polymyositis/dermatomyositis are strongly associated with a broad range of malignancies, which could contribute to the increased risk of opportunistic infections through the use of cytotoxic anti-cancer therapies.

“Careful observation and preventive therapy for opportunistic infections may be warranted in selected polymyositis/dermatomyositis patients, especially during the first year after the diagnosis,” the authors wrote.

REFERENCE

Chung-Yuan Hsu, Chi-Hua Ko, Jiun-Ling Wang, et al. “Comparing the burdens of opportunistic infections among patients with systemic rheumatic diseases: a nationally representative cohort study.” Arthritis Res Ther. October 12, 2019. doi: 10.1186/s13075-019-1997-5.