High Frequency of Specific Polysaccharide Antibody Deficiency in Adults With Unexplained, Recurrent and/or Severe Infections With Encapsulated Bacteria.

This article focuses on evaluating a systematic screening strategy for primary immunodeficiencies (PIDs) in adults presenting with unexplained recurrent and/or severe bacterial infections, with particular emphasis on specific polysaccharide antibody deficiency (SPAD). In a prospective multicenter study of 118 adults without known predisposing factors, PIDs were diagnosed in 39.8% of cases, with SPAD accounting for 78.7% of these diagnoses. SPAD patients exhibited recurrent respiratory tract infections or invasive infections caused by encapsulated bacteria and were managed with conjugate vaccines, preventive antibiotics, and immunoglobulin replacement therapy (IgRT), the latter showing marked effectiveness in reducing infections. The study suggests that SPAD screening should be considered in adults with unexplained bacterial infections after excluding other PIDs, and that IgRT may be a beneficial treatment for SPAD-associated recurrent infections.