title: A novel mutation in the complement component 3 gene in a patient with selective IgA deficiency.
abstract: OBJECTIVE
  Immunological and molecular evaluation of a patient presenting with recurrent infections caused by Streptococcus pneumoniae and low complement component 3 (C3) levels.
  
  
  METHODS
  Immunological evaluation included complement components and immunoglobulin level quantification as well as number and function of T cells, B cells and neutrophils. Serotype-specific immunoglobulin G antibodies against S. pneumoniae capsular polysaccharides were quantified by ELISA in serum samples before and after vaccination with unconjugated polysaccharide vaccine. For the molecular analysis, genomic DNA from the patient and parents were isolated and all exons as well as exon-intron boundaries of the C3 gene were sequenced by Sanger sequencing.
  
  
  RESULTS
  A 16-year-old male, born to consanguineous parents, presented with recurrent episodes of pneumonia caused by S. pneumoniae and bronchiectasis. The patient showed severely reduced C3 and immunoglobulin A levels, while the parents showed moderately reduced levels of C3. Mutational analysis revealed a novel, homozygous missense mutation in the C3 gene (c. C4554G, p. Cys1518Trp), substituting a highly conserved amino acid in the C345C domain of C3 and interrupting one of its disulfide bonds. Both parents were found to be carriers of the affected allele. Vaccination against S. pneumoniae resulted in considerable clinical improvement.
  
  
  CONCLUSIONS
  We report a novel homozygous mutation in the C3 gene in a patient with concomitant selective IgA deficiency who presented with a marked clinical improvement after vaccination against S. pneumoniae. This observation underlines the notion that vaccination against this microorganism is an important strategy for treatment of PID patients, particularly those presenting with increased susceptibility to infections caused by this agent.
authors.affiliation: CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, AKH BT 25.3, A-1090, Vienna, Austria.
authors.forename: Elisangela
authors.initials: E
authors.lastname: Santos-Valente
authors.forename: Ismail
authors.initials: I
authors.lastname: Reisli
authors.forename: Hasibe
authors.initials: H
authors.lastname: Artaç
authors.forename: Raphael
authors.initials: R
authors.lastname: Ott
authors.forename: Özden
authors.initials: Ö
authors.lastname: Sanal
authors.forename: Kaan
authors.initials: K
authors.lastname: Boztug
mesh_terms: D000293:Adolescent; D001987:Bronchiectasis / Q000150:complications / Q000235:genetics / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D003176:Complement C3 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D006801:Humans; D017098:IgA Deficiency / Q000150:complications / Q000235:genetics* / Q000276:immunology*; D008297:Male; D020125:Mutation, Missense / Q000235:genetics / Q000276:immunology; D010375:Pedigree; D022242:Pneumococcal Vaccines / Q000627:therapeutic use; D011018:Pneumonia, Pneumococcal / Q000235:genetics / Q000276:immunology / Q000517:prevention & control; D017354:Point Mutation / Q000235:genetics / Q000276:immunology; D017386:Sequence Homology, Amino Acid
chemical_list: D003176:Complement C3; D022242:Pneumococcal Vaccines