Background Idiopathic inflammatory myopathies, also known as myositis, are a heterogeneous group of acquired diseases of probable autoimmune origin, characterized by the presence of inflammatory muscle infiltrates.Infectious complications are not uncommon in myositis, and some predisposing factors, such as upper esophageal involvement, calcinosis cutis, ventilatory insufficiency due to diaphragm involvement, and immunosuppressive drug therapies, seem to be implicated.

Objectives To describe the prevalence, clinical characteristics, and risk factors for opportunistic infection (OI) in a cohort of patients with inflammatory myopathies, and compare mortality rates between those with and without OIs.

Methods In total, 204 patients from our myositis cohort were reviewed to identify patients who had experienced an OI during the period 1986–2014. The patients' clinical characteristics, treatment received, and outcome were systematically recorded. Disease activity at the OI diagnosis and cumulative doses of immunosuppressive drugs were analyzed, as well as the specific pathogens involved and affected organs.

Results The prevalence of OI in the total cohort, was 6.4%: viruses, 44.4% (varicella-zoster virus, cytomegalovirus); bacteria, 22.2% (Salmonella sp., Mycobacterium tuberculosis, M. chelonae); fungi, 16.7% (Candida albicans, Pneumocystis jirovecii); and parasites, 16.7% (Toxoplamosis gondii, Leishmania spp.) were the pathogens detected. Lung and skin/soft tissues were the organs most commonly affected (27.8%). Overall, 55.6% of OIs developed during the first year after the myositis diagnosis and were significantly associated with administration of high-dose glucocorticoids (p=0.0148). Fever at onset of myositis (p=0.0317), biological therapy (p<0.001) and sequential administration of 4 or more immunosuppressive agents during myositis evolution (p=0.0032) were significantly associated with OI. All-cause mortality in the OI group was 3.69 deaths per 100 patients/year versus 3.40 in the remainder of the cohort (p=0.996).

Conclusions The prevalence of OI was 6.4% in our myositis cohort. High-dose glucocorticoids at disease onset and severe immunosuppression are implicated in the development of these complications. Mortality did not differ from the remainder of the cohort.

Disclosure of Interest None declared