Effects of AE-ILD in Patients With Idiopathic Inflammatory Myopathy

Acute exacerbation of interstitial lung disease (AE-ILD) is a less frequent but fatal complication in patients with idiopathic inflammatory myopathy (IIM), although a regimen of steroids and disease-modifying antirheumatic drugs (DMARDs) was found to reduce short-term death rates, according to a new study published in the Rheumatology section of Frontiers in Medicine.

Investigators from China retrospectively observed patients with IIM admitted to a hospital between 2007 and 2019 to understand the prevalence, risk factors, outcome, and outcome-related factors of AE-ILD in patients with IIM. Those patients formed the case group and then were matched with a control group of patients with IIM without AE-ILD by age and sex. They were further divided into groups of patients who died in hospital or within 2 weeks of discharge (the mortality group) or those who survived after 2 weeks hospital discharge (survival group). The adult patients involved in the analysis had dermatomyositis (DM), polymyositis (PM), and clinically amyopathic dermatomyositis (CADM) and presented related risk factors for AE-ILD.

AE-ILD was mostly studied in patients with idiopathic pulmonary fibrosis, the study authors said, but it has also recently been noted in patients with connective tissue disease (CTD). The lifetime incidence of AE-ILD in patients with CTD was about 7.2%, they said.

The investigators reviewed the patients’ electronic health records to gather demographic and disease information. The study authors also noted that in the absence of diagnostic criteria for AE-ILD in patients with CTD, they used adopted criteria based on studies examining acute exacerbation of idiopathic pulmonary fibrosis. These criteria included previous or concurrent diagnosis of ILD, acute worsening or development of dyspnea typically less than 1 month’s duration, computed tomography with new bilateral ground-glass opacity and/or consolidation superimposed on a background pattern consistent with usual interstitial pneumonia pattern, and deterioration not fully explained by cardiac failure or fluid overload.

Of 665 patients with DM, PM, or CADM admitted to the hospital during the study period, 483 were identified as having the complication of ILD. Eventually, 64 of 665 patients were diagnosed with AE-ILD while they were in the hospital, the study authors found. The average age for AE-ILD patients was about 57 years, which was significantly higher than the patients without AE-ILD (53 years).

The incidence of AE-ILD in patients with DM, PM, and CADM, respectively, was 10.8%, 5.7%, and 19.4%, the study authors found. The short-term mortality rate for patients with AE-ILD was 39.1% compared with 5.7% among those without AE-ILD, the investigators said. A quarter of the case group died in hospital or within 2 weeks of hospital discharge, they added.

When comparing the 64 patients with AE-ILD and 128 matched patients without AE-ILD, the study authors found that the case group presented with significantly higher on-admission disease activity compared with the controls. The case group also presented with lower level of percent-predicted diffusing capacity of the lung for carbon monoxide (DLCO%).

They also found that bacterial and fungal infections were the 2 most common infections among the patients with AE-ILD, at 21.9% and 23.4%, respectively. The most commonly used therapy was a combined steroid and DMARDs, and mycophenolate mofetil was the most frequently used DMARD in this combination therapy. It was used in about half of the instances.

“In spite of all the limitations, we intended to shed some light on the future study of AE-ILD in patients with DM, PM, or CADM,” the study authors concluded. “Elevated on-admission disease activity, lower DLCO% and diagnosis of CADM were found to be risk factor[s] for development of AE-ILD in patients with DM, PM, or CADM.…A therapeutic regimen of steroid and DMARDs was found to reduce short-term death in IIM patients with AE-ILD.”

Reference

Liang J, Cao H, Ke Y, Sun C, Chen W, Lin J. Acute exacerbation of interstitial lung disease in adult patients with idiopathic inflammatory myopathies: a retrospective case-control study [published online January 31, 2020]. Front Med. doi: 10.3389/fmed.2020.00012.