Adding immunoglobulin to steroids improved new-onset myositis in a small trial

Adding intravenous immunoglobulin to standard high-dose steroids helped patients with newly diagnosed inflammatory muscle disease improve faster and more completely than steroids alone, in a small randomised trial published in JAMA Neurology [s1]. The effect was real but the evidence is thin: the trial ran at a single Dutch referral centre and its primary result rests on 42 patients who reached the 12-week endpoint [s1].

Idiopathic inflammatory myopathies — a group that includes dermatomyositis and related conditions — are autoimmune diseases in which the immune system attacks muscle, causing progressive weakness and, in some forms, skin, lung or heart involvement. The first-line treatment is high-dose corticosteroids, which work but carry a heavy toll of side effects and do not help everyone. Immunoglobulin, a pooled-antibody product infused into the vein, is already used in some myositis, and the trial set out to test whether giving it up front, alongside steroids in patients just diagnosed, would add benefit [s1].

What the trial found

The TIME IS MUSCLE trial enrolled adults with newly diagnosed disease and little or no prior immunosuppressive treatment, at a tertiary myositis centre between September 2021 and September 2025 [s1][s2]. All started standard high-dose prednisone — 1 mg per kilogram per day, capped at 80 mg — and were randomised 1:1 to add either immunoglobulin at 2.0 g per kilogram or a matching placebo at weeks 0, 4 and 8 [s1]. Of 44 patients included (mean age 58.7 years, half female), 42 reached the primary endpoint: 23 in the immunoglobulin group and 19 on placebo [s1].

The primary measure was the Total Improvement Score, a weighted composite of six standard myositis-activity measures on a 0-to-100 scale in which higher means more improvement. At 12 weeks it averaged 60.0 (95% confidence interval, 52.6 to 67.4) with immunoglobulin against 42.5 (30.6 to 54.4) on placebo, a statistically significant difference (P = 0.01) [s1]. The gap widened at the thresholds clinicians care about: moderate-or-better improvement was reached by 91% of the immunoglobulin group versus 53% on placebo (P = 0.01), and major improvement by 70% versus 26% (P = 0.005) [s1]. Patients on immunoglobulin also improved sooner — a median of 4 weeks to a moderate response, against 12 weeks on placebo (P = 0.005) [s1]. On safety, the trial reported one asymptomatic deep-vein clot in the immunoglobulin group and no other notable signal [s1].

How much weight it can bear

The direction is consistent and the effect sizes are large, but three limits keep this from being practice-changing on its own. The trial is small — 42 analysed patients — and the confidence intervals are correspondingly wide; the lower bound of the placebo group's improvement score, 30.6, sits well below the immunoglobulin group's 52.6, but with numbers this size a single centre's case mix can move the result [s1]. It was conducted at one referral hospital, so whether the benefit generalises to community practice and to the full diversity of these diseases — which range from dermatomyositis to necrotising and antisynthetase forms — is untested here [s1].

And the primary endpoint is a 12-week activity score, not a hard outcome. Faster improvement matters to patients living with weakness, and getting more people to a major response early is a genuine clinical goal, but the trial does not show whether the early advantage translates into less long-term disability, fewer relapses, or a lower cumulative steroid dose — the outcome that would most justify adding an expensive, blood-derived infusion to first-line care [s1]. Immunoglobulin is also a scarce, donor-dependent product, which makes the case for using it earlier and more widely one that has to clear a higher bar than efficacy alone.

What the study does establish is a credible, blinded signal that front-loading immunoglobulin accelerates recovery in new-onset myositis — the kind of result that earns a larger, multi-centre trial rather than settles the question. It joins a broader effort to move autoimmune and rheumatic disease beyond broad immunosuppression toward more targeted intervention, and beyond decades-old drugs toward treatments built for the mechanism. This article describes trial findings and is not medical advice.

Sources

• Intravenous Immunoglobulin Add-On in Newly Diagnosed Idiopathic Inflammatory Myopathies — JAMA Neurology, published online 14 September 2026
• TIME IS MUSCLE trial registration (EudraCT 2020-001710-37) — EU Clinical Trials Register