Treatment with high-dose recombinant human hyaluronidase-facilitated subcutaneous immune globulins in patients with juvenile dermatomyositis who are intolerant to intravenous immune globulins: a report of 5 cases

High-dose intravenous immune globulins (IVIg) are frequently used in refractory juvenile dermatomyositis (JDM) but are often poorly tolerated. High-dose recombinant human hyaluronidase-facilitated subcutaneous immune globulins (fSCIg) allow the administration of much higher doses of immune globulins than conventional subcutaneous immune globulin therapy and may be an alternative to IVIg. The safety and efficacy of fSCIg therapy in JDM is unknown.

In this retrospective case series, five patients with steroid-refractory severe JDM were treated with high-dose fSCIg due to IVIg adverse effects (severe headaches, nausea, vomiting, difficult venous access). Peak serum IgG levels, muscle enzymes, the childhood myositis assessment scale and adverse effects were retrieved for at least 6 months following intiation of fSCIg. Data were analyzed by descriptive statistics.

Patients initially received fSCIg 1 g/kg every 14 days, resulting in median IgG peak levels of 1901 mg/dl (1606–2719 mg/dl), compared to median IgG peak and trough levels while previously receiving IVIg of 2741 mg/dl (2429–2849 mg/dl) and 1351 mg/dl (1156–1710 mg/dl). Additional antirheumatic therapies consisted of low-dose glucocorticoid therapy, methotrexate, mycophenolate mofetil and/or rituximab. Two patients maintained clinically inactive disease and three patients had only a partial treatment response. In the three patients with partial treatment response, fSCIg 1 g/kg was then given on days 1 and 6 of every 28-day cycle resulting in IgG peak levels of between 2300–2846 mg/dl (previously 1606–1901 mg/dl on the biweekly regimen), resulting in clinically inactive disease in two of the three patients. There were no relevant adverse effects that limited continuation of fSCIg treatment.

High-dose fSCIg is well-tolerated in patients with JDM and high peak serum IgG levels can be achieved which may be important for treatment success. High-dose fSCIg may therefore be an alternative to high-dose IVIg and deserves further study.

This is a case series and data were retrospectively registered.