Background: Dermatomyositis (DM)/polymyositis (PM) is a systemic autoimmune disease characterized by proximal limb muscle with high morbidity and mortality and poor prognosis mediated by immune dysfunction; its etiology is unknown. DM/PM patients are at excessive risk of interstitial lung disease (ILD) and a higher risk of death. However, the role of circulating lymphocyte subsets, which play a pivotal role in occurrence and progression of DM/PM and ILD, respectively, remains unclear in DM/PM patients with ILD.
Methods: Demographic characteristics, general data, and peripheral lymphocyte levels measured by flow cytometry were collected and analyzed in 47 DM/PM patients with ILD, 65 patients without ILD, and 105 healthy controls (HCs).
Results: The most important first symptom of DM/PM patients is rash. Compared with non-ILD patients, the levels of neutrophil/lymphocyte ratio (NLR), systemic inflammatory response index (SIRI) were significantly higher and the levels of C reactive protein (CRP) were significantly lower in patients with ILD. Compared with HCs, DM/PM patients, with or without ILD, had decreased absolute counts of T, CD4 + T, CD8 + T, natural killer (NK), helper T (Th) 1, Th2, Th17, and regulatory T (Treg)cells. The fewest Th1 and Treg cells and the the lowest CD8 + T and Th1 cells percentages were seen in peripheral blood of patients with ILD. Longer duration, decreased lymphocyte/monocyte ratio (LMR)levels and CD8 + T and Th1 cells proportions, and fewer circulating Treg cells were independent risk factors for DM/PM with ILD.
Conclusions: The identification of peripheral blood T lymphocyte subsets, especially Treg cells, and blood count in DM/PM appears to be useful in the comprehensive assessment of clinical lung involvement.
Keywords: Polymyositis; Treg cells; dermatomyositis; interstitial lung disease; risk factors.