Symptomatic Primary Selective Immunoglobulin M Deficiency with Nonprotective Pneumococcal Titers Responsive to Subcutaneous Immunoglobulin Treatment.

Selective immunoglobulin M deficiency (SIgMD) is a rare disorder with varying clinical features. The prevalence of SIgMD is 0.03-3%. Patients may be asymptomatic or else present with recurrent infection, autoimmunity, atopic disease and/or malignancy. About 50% of patients with symptomatic SIgMD also have impaired antibody responses to the pneumococcal polysaccharide vaccine. We report on an adult who presented with symptomatic SIgMD with impaired pneumococcal polysaccharide antibody responses and lymphopenia, who experienced a significant clinical improvement in the frequency of infections after subcutaneous immunoglobulin replacement therapy.