Complement Factor I Deficiency Associated With Recurrent Infections, Vasculitis and Immune Complex Glomerulonephritis

Scand J Infect Dis. 2005;37(8):615-618. doi: 10.1080/00365540510034536.


Here we report complement factor I deficiency in an 11-y-old girl from a consanguineous Turkish family, who presented with recurrent pyogenic infections, vasculitic eruptions and immune complex glomerulonephritis. A moderately low C3 level together with the clinical picture suggested a deficiency affecting regulation of complement activation. Analysis of haemolytic activity revealed absence of alternative pathway activity and subsequent analysis showed no detectable factor I (<2%) together with a low level of factor B and a moderately low level of factor H, indicating consumption secondary to the factor I deficiency. Factor I inhibits complement activation beyond C3 by cleavage of C3b in the presence of cofactors. Complement factor I deficiency is frequently associated with recurrent pyogenic infections mainly affecting the upper and lower respiratory tract, or presenting as meningitis or septicaemia, while rheumatic disorders have not been a prominent feature. The patient's sister also suffered from recurrent pyogenic infections and had a low C3 level clearly suggesting the same deficiency.

Publication types

  • Case Reports

MeSH terms

  • Adolescent
  • Child
  • Complement Factor I / deficiency*
  • Consanguinity
  • Female
  • Glomerulonephritis / complications*
  • Glomerulonephritis / immunology
  • Humans
  • Infections / complications*
  • Recurrence
  • Turkey
  • Vasculitis / complications*


  • Complement Factor I