Background/Purpose:

Intravenous immunoglobulin (IVIg) therapy is recommended for patients suffering from inflammatory myopathies refractory to corticosteroids and immunosuppressive drugs. It is also recommended for patients with myositis who are unable to continue immunosuppression due to adverse reactions (ADRs) or for whom such immunosuppressive therapy is contraindicated. However, long-term IVIg therapy is associated with a risk of systemic adverse reactions, and is also associated with the need of intravenous access, surveillance and hospitalizations. Therefore, employing an alternative route of administration, subcutaneous immunoglobulin (SCIg) was made available. For the majority of patients, IVIg and SCIg are equally efficacious; however, they are not equally exchangeable. 

Methods:

A retrospective analysis studied compliance, tolerance and effectiveness (using muscle testing, muscle disability scale and enzyme CK) of a 16,5% SCIg therapy in inflammatory myopathies. Between August 2011 and February 2015, 19 patients were enrolled: 10 with polymyositis (PM), 2 with dermatomyositis (DM) and 7 with inclusion body myositis (IBM). 

Results:

Patients on SCIg therapy were followed on average 16.9 months (range: 1 to 42 months). Reasons to switch to the subcutaneous route were: patients being more independent (14/19), therapeutic failure (3/19), end dose effect (1/19), and poor venous access (1/19). Ten of 19 patients previously received IVIg. Average dose of SCIg was 1.7 [±0.4] g/kg/month. General regimen of SCIg treatment included two weekly administrations totalling 130.0 [±73.0] mL/week. Maximally 25 mL/site were infused at 4 sites each. All patients were followed by home delivery companies. Any deviations from the physician-defined protocol were recorded. Regarding treatment efficacy, data on muscle testing and/or functional scale were available for 9 of 12 PM/DM patients. All of these patients significantly improved (p>0,05), and 3 of them had normalized testing (88/88 on muscular testing). In IBM patients, no significant improvement was expected but 4 patients stabilized under SCIg therapy, and 2 patients with initial dysphagia recovered. Ten of 19 patients experienced adverse reactions during the follow-up period. Local reactions (skin rash, swelling, redness, induration, pain or reflux at injection site) and systemic reactions (headache, chills, hot flushes, high blood pressure, dizziness and tiredness) were reported. These ADRs resolved after decreasing the infusion rate, dose adapting or using premedication.

Conclusion:

In all patients, the use of SCIg was feasible and well-tolerated during long-term therapy. Furthermore, relevant improvement in muscle strength was observed in 8 of 14 patients. SCIg therapy allowed for reducing the daily corticoisteroid use in 3 patients and stopping the immunosuppressant therapy in 2 patients. These observations suggest that SCIg could be used as an alternative route to IVIg in auto-immune diseases.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/use-of-long-term-subscutaneous-immunoglobulins-in-inflammatory-myopathies-a-retrospective-analysis-of-19-patients/