Effectiveness of Subcutaneous IgG Supplementation in a Patient with Myotonic Dystrophy

Rationale: Myotonic dystrophy (MyD) is an autosomal dominant neuromuscular disease associated with a variety of systemic abnormalities including low concentrations of serum IgG. Optimal management of hypo-IgG in patients suffering from MyD still needs to be defined. In primary immunodeficiencies, lower total weekly SCIG doses are required to achieve equivalent serum IgG levels than with monthly IVIG therapy.

Methods: Immunoglobulin supplementation and mesurement of trough/steady-state serum IgG level

Results:  We report the effectiveness of subcutaneous IgG supplementation in a female patient with myotonic dystrophy and low IgG plasma levels (2.79 g/L) likely due to high IgG catabolism. Over the course of her illness, the patient experienced recurrent infections. Initial treatment with intravenous immunoglobulin (IVIG) resulted in a variety of unfavourable side effects, likely due to high requirements (0.75 g/kg/month) to achieve adequate IgG serum level. The patient was subsequently switched to subcutaneous IgG (SCIG). Adequate IgG serum level was achieved with a dose of 100 mg/kg/week without side effect. Since the start of IgG supplementation, no infections were reported. 

Conclusions: Subcutaneous once-weekly IgG administration appears to be more effective than once-monthly IVIG regimen in a patient with high IgG catabolism.