A Novel Case of Complement Factor B Deficiency
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LETTER TO EDITOR
A Novel Case of Complement Factor B Deficiency Amélie Gauthier 1
&
Eric Wagner 2 & Roseline Thibeault 3 & Aubert Lavoie 1
Received: 16 May 2020 / Accepted: 30 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
To the Editor, Complement deficiencies comprise between 1 and 7% of all primary immunodeficiencies [1]. Of these, defects in proteins specific to the classical and terminal pathways are more frequent than deficiencies in the components of the alternative pathway, namely, properdin, factor D, and factor B, which account for only 2.5% of all complement deficiencies [1]. Properdin deficiency, reported to be present in 100 to 500 individuals, is inherited in an X-linked pattern [2]. It is associated with fulminant meningococcal disease. Factor D deficiency, inherited in an autosomal recessive pattern, is also described as a predisposing factor for meningococcal infection with less than 10 reported cases. Factor B deficiency has been described only once, in a 32-year-old woman. She presented with recurrent pneumococcal and meningococcal infections [3]. We describe here a novel case of factor B deficiency. An 8-year-old boy was born at term from an uncomplicated pregnancy. Both parents are French Canadians, healthy, and unrelated. The patient has two younger sisters and two younger brothers. The vaccination schedule was up to date. Medical history is remarkable for repeated pneumococcal infections starting with a pneumococcal bacteremia at 4 months of age. The patient suffered a periorbital cellulitis at 5 months of age. At 11 months, he presented with pneumococcal meningitis and bacteremia. He was then disease free until he had tonsillopharyngitis 4 years later. A few months later, he had a * Amélie Gauthier [email protected] 1
Department of Allergy and Immunology, CHU de Québec-CHUL, Laval University Hospital Center, Laval University, Quebec City G1V 4G2, Canada
2
Immunology and Histocompatibility Laboratory, CHU de Québec-Université Laval and Department of Microbiology-Infectiology and Immunology, Laval University, Quebec City, QC G1V 4G2, Canada
3
Department of Pediatrics, CHU de Québec-CHUL, Laval University, Quebec City G1V 4G2, Canada
right superior lobe pneumonia with empyema caused by Streptococcus pneumoniae. His most recent infection, at 8 years of age, was a pneumonia with septic shock and acute respiratory distress syndrome. He was intubated for 9 days and put under mechanical ventilation. He also needed 7 days of extracorporeal membrane oxygenation. He suffered from thromboembolism of his right femoral artery and had a partial first toe amputation. Unfortunately, no bacteria were identified on that occasion. An immunological workup showed the following: normal complete blood count and differential; normal T, B, and NK lymphocyte subpopulations; normal IgG, IgA, and IgM levels; normal classical complement pathway activity; and normal C3 and C4 levels (Table 1). MBL pathway activity was within the normal range. Alternative complement p
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