Selective IgM Deficiency (SIgMD) is a recently incorporated disorder in the classification of primary immunodeficiency diseases. The purpose of this study was to present detailed clinical and immunological features in a cohort of 62 adult patients with SIgMD. A retrospective chart review of 62 patients between 2009 and 2017 with a diagnosis of SIgMD was performed for clinical and immunological features, and response to immunoglobulin therapy in symptomatic patients who also exhibited specific antibody deficiency. The majority of patients presented with recurrent and chronic upper and lower respiratory tract infections (73%), most often with recurrent sinusitis (29%), bronchitis (33%), pneumonia (21%), and recurrent urinary tract infections (16%). Forty three percent of patients had associated autoimmune diseases including Hashimoto’s thyroiditis, and systemic lupus erythematosus. Approximately 35% of patients had atopic diseases, including allergic rhinitis and asthma. CD3+ T, CD4+ T, CD8+ T, and CD19+ B cells were normal in the majority of patients. IgG subclass deficiency was observed in approximately 22% of cases. Forty seven percent of patients exhibited specific anti-pneumococcal antibody deficiency. The six most common pneumococcal serotypes that were impaired in majority (>70%) of subjects included 3, 4, 9V, 9N, 12F, 23F. Eighteen (66%) of 27 patients with specific antibody deficiency received immunoglobulin therapy and almost all subjects responded to immunoglobulin therapy by decreased frequency of infections. No correlation was observed in immunological features, clinical manifestations, or response to therapy with serum IgM levels.
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