Deficiency in Complement Factor B

A genetic deficiency of factor B confirms the role of the protein in the activation of the alternative complement pathway in humans and in protection against infection by encapsulated bacteria.To the Editor: The alternative complement pathway is essential for defense against infection by polysaccharide-encapsulated bacteria. Factor B, factor D, and properdin are required to stably initiate the process.(1) Deficiencies of factor D and properdin have been described in humans.(2)-(4) Here, we describe a 32-year-old woman with recurrent pneumococcal and meningococcal infection in whom factor B deficiency was detected. The patient had nonconsanguineous parents of English and Scottish heritage. Her medical history revealed four clinically significant infections dating from childhood. At 2 years of age, she had primary pneumococcal peritonitis. Two years later, she was treated for community-acquired pneumonia. ...