There are presently no biomarkers for disease activity and damage accumulation in idiopathic inflammatory myopathies (IIMs). For a cross-sectional study, researchers sought to assess the link between low-density granulocytes (LDGs), neutrophil extracellular traps (NETs), and clinical and immunological characteristics in IIM patients.

In 65 adult patients with IIM, they examined disease activity, damage accrual, the number of LDGs, NETs, LL-37 expression, and serum cytokines. Kruskal-Wallis, Mann-Whitney U, and Spearman correlation tests were used to analyze group differences and correlations. Logistic regression was used to examine the relationship between LDGs, NETs, disease activity, calcinosis, and cutaneous ulcers. They utilized receiving operating characteristic curves to investigate the ability of LDGs and NETs to detect disease activity. 

Patients with active illness, ulcers, calcinosis, and anti–MDA5 antibodies had greater amounts of low-density granulocytes, which were associated with blood levels of IL-17A and IL-18. Patients with calcinosis had increased neutrophil extracellular traps, higher antinuclear antibody titers, and positive anti-PM/Scl75 tests. The occurrence of calcinosis and cutaneous ulcers was related to a high proportion of both total LDGs and NETs. The concentration of LL-37 was greater in NETs coming from LDGs. Patients with active dermatomyositis had higher levels of normal-density neutrophils.

Patients with IIM with active illness had an increase in low-density granulocytes and NETs carrying LL-37, which correlates with proinflammatory cytokines. Total and CD10+ LDGs are both possible biomarkers for disease activity and, when combined with NETs, have the ability to identify individuals at risk for cutaneous ulcers and calcinosis.