Myotonic dystrophy type 1 (DM1) or Steinert’s disease, is a genetically determined disorder belonging to the group of muscle dystrophies. DM1 is mainly characterized by myotonia and progressive weakness and atrophy of skeletal muscles. Patients are heterogeneously affected by the disease varying from having only slight clinical signs to being fully handicapped. Pneumonia is an important primary and secondary cause of death in DM1 patients. Due to muscle weakness there is an increased susceptibility to mainly respiratory infections, however another factor may be hypogammaglobulinaemia as reported in 40-50% of DM1 patients. Remarkably to date no data can be found about the nature and impact of hypogammaglobulinemia on infection rate in these patients.
Methods
The immune status was evaluated and retrospective data analysis was performed of 17 DM1 patients. Standard screening comprised a questionnaire about (recurrent) infections, frequent use of antibiotics and hospital stays due to infections. Standard laboratory tests comprised serum IgA, IgM, IgG and IgG subclasses, NK, B and T cell counts, granulocyte, leucocyte and monocyte counts by FACS analysis. Also a vaccination response test was performed.
Results
The majority of the patients (71%) had hypogammaglobulinemia (IgG<7 g/L) ranging from 3.9 g/l and 6.5 g/l. Strikingly, IgG1 was selectively below normal range in fifteen out of sixteen patients (94%). None of the patients were on immune suppressive medication. The overall rate of pneumonia was 53%. Nine out of seventeen patients suffered from pneumonia at least once between January 2000 and October 2012, four of those patients had recurrent pneumonia or sinopulmonal infections. Other infections also occurred, e.g. recurrent urinary tract infection, recurrent facial herpes simplex and erysipelas. In the patients with hypoglobulinemia the rate of pneumonia was 58% compared to 40% in patients whose total IgG was normal (p = 0,52). Interestingly three patients with low IgG serum levels also showed insufficient vaccination responses for H. influenzae type B and/or S. pneumoniae. Two of which had recurrent infections, including pneumonia. These patients met the criteria for common variable immune deficiency (CVID).
Discussion
Our statistical data are limited due to the small number of patients included in this pilot study. However, the results are astounding with 94% having an IgG1 deficiency and 71% hypogammaglobulinemia. These results imply that screening for immune deficiency should be part of standard care for patients with DM1, however studies are warranted to investigate if IgG substitution therapy may lead to a decrease in infections and improving the quality of life.