4 Hypogammaglobulinemia and infection risk in myotonic dystrophy type 1

Background/ObjectivesHypogammaglobulinemia is a common yet under-recognised feature of myotonic dystrophy type 1 (DM1). The aims of our study were to assess whether low immunoglobulin G (IgG) levels are associated with an increased risk of infection in DM1 patients and to ascertain the association between immunoglobulin levels and cytosine-thymine-guanine (CTG) repeat length in the DMPK gene.MethodsWe conducted a single-centre, retrospective cross-sectional study of 65 adult patients with DM1 to determine the frequency of IgG deficiency, the association with CTG repeat expansion size, and the infection risk profile.ResultsForty one percent (41%) of DM1 patients had IgG deficiency despite normal lymphocyte, IgA, IgM, and albumin levels. There was an association between CTG repeat expansion size and the degree of IgG deficiency (F = 6.3, p-value 0.020). There was no association between IgG deficiency and frequency of infection in this group (p-value 0.428). Most infections were aspiration pneumonia with evidence of oropharyngeal dysphagia on swallow assessment.DiscussionIgG deficiency is a frequent occurrence in DM1 patients and is associated with increasing CTG repeat expansion size. Reduced IgG levels were not associated with increased infection frequency. Routine monitoring of IgG levels and immunoglobulin supplementation in DM1 patients may not be necessary unless there is an unexplained history of recurrent infections.