title: Complement factor I deficiency associated with recurrent infections, vasculitis and immune complex glomerulonephritis.
abstract: 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.
authors.affiliation: ferahgen@yahoo.com
authors.forename: Ferah
authors.initials: F
authors.lastname: Genel
authors.forename: Anders G
authors.initials: AG
authors.lastname: Sjöholm
authors.forename: Lillemor
authors.initials: L
authors.lastname: Skattum
authors.forename: Lennart
authors.initials: L
authors.lastname: Truedsson
mesh_terms: D000293:Adolescent; D002648:Child; D017244:Complement Factor I / Q000172:deficiency*; D003241:Consanguinity; D005260:Female; D005921:Glomerulonephritis / Q000150:complications* / Q000276:immunology; D006801:Humans; D007239:Infections / Q000150:complications*; D012008:Recurrence; D014421:Turkey; D014657:Vasculitis / Q000150:complications*
chemical_list: D017244:Complement Factor I