Subcutaneous immunoglobulin for patients with idiopathic inflammatory myopathies: a real-world, single-centre...

Idiopathic inflammatory myopathies (IIMs) are heterogeneous diseases characterized by skeletal muscle inflammation associated with cutaneous, pulmonary and/or other visceral organ involvement. IVIG has been recommended as an adjunct therapy for IIM patients refractory to conventional therapy. However, IVIG has high resource needs and increased risk of adverse reactions. Subcutaneous immunoglobulin (SCIG) therapy has been used as an alternative to IVIG in primary immunodeficiencies and neuroinflammatory disorders. We assessed the satisfaction, patient preference and effectiveness in IIM patients who transitioned from IVIG to SCIG.

We retrospectively reviewed consecutive 20 patients with IIM who were transitioned from IVIG to SCIG therapy for >12 months. Patient preference between IVIG and SCIG was surveyed using a questionnaire previously used in studies of neuroinflammatory conditions. In addition, disease flares, changes in immunosuppression, cumulative prednisone doses and global disease activity were evaluated using the Myositis Intention to Treat Index (MITAX) 12 months pre- and post-SCIG initiation.

Most patients (78.9%) preferred SCIG over IVIG and preferred home-based therapies to hospital-based therapies. There was no significant difference in global disease activity (MITAX 3.31 vs 3.02) or in cumulative steroid doses 12 months pre- or post-SCIG initiation. Three patients experienced disease flares, five escalated in immunosuppression, while four patients deescalated in immunosuppressive medications.

SCIG is preferred by most patients over IVIG without a substantial increased disease activity or need for additional CS. Future cost-effectiveness studies may provide an additional rationale for utilizing SCIG over IVIG for maintenance therapy for IIM.