Post-hoc analysis to assess the effect of intravenous immunoglobulin (IVIg) on pulmonary symptoms of dermatomyositis (DM).

Pulmonary manifestations, including interstitial lung disease (ILD), are a major cause of mortality and morbidity in DM patients. The ProDERM study evaluated efficacy of IVIg in adult DM patients.

ProDERM was a placebo-controlled, double-blind, multicenter Phase 3 study. For Weeks 0–16, patients were randomized to 2.0 g/kg IVIg or placebo every 4 weeks. For Weeks 16–40, all eligible patients received IVIg (open-label) for six additional cycles. DM pulmonary symptoms were assessed using the Myositis Disease Activity Assessment Tool (MDAAT). Visual analog scales (VAS) scored overall pulmonary disease activity over 10 cm (higher scores indicated worse disease). Physicians also recorded dysphonia, active reversible ILD, and dyspnea using MDAAT. To avoid floor effect, treatment effect was analyzed only in patients with baseline VAS >0.5 cm.

Of 95 DM patients in ProDERM, 36 (37.9%) had baseline pulmonary VAS >0.5 cm, indicating myositis lung involvement. By Week 40, this decreased to 20/88 patients with available data (22.7%; p=0.007). For patients with data at baseline and Week 16, those on IVIg (n=12) experienced a mean decrease of 1.15 cm (37.7%; p=0.001) vs. 0.17 cm (6.5%) in patients on placebo (n=21; p=0.50). From baseline to Week 40, with placebo patients having switched to IVIg, the mean decrease for the combined cohort with available data (n=32 patients) was 1.08 cm (38.2%; p<0.001).

The percentage of patients with dysphonia decreased from 20% at baseline to 8% at Week 40 (p=0.04). The percentages with dyspnea or ILD decreased numerically from baseline to Weeks 16 and 40 (not statistically significant).

IVIg may have favorable treatment effects on active pulmonary manifestations of DM. Further studies are warranted.