Case report: lupus nephritis with autoantibodies to complement alternative pathway proteins and C3 gene mutation

BMC Nephrol. 2015 Mar 30:16:40. doi: 10.1186/s12882-015-0032-6.

Abstract

Background: Glomerulonephritis is one of the most severe complications of lupus, a systemic disease with multi-organ involvement, with tissue damage produced mainly by complement activation. As a result of this activation, patients with active lupus present hypocomplementemia during disease flares, but C3 and C4 levels are recovered between episodes.

Case presentation: We present a patient who suffered two lupus nephritis episodes in 5 years, achieving complete remission with treatment after both of them, but with C3 levels persistently below normal range. Genetic study revealed that the patient carried a mutation in heterozygosis in the C3 gene. Serial sera samples were analyzed, and autoantibodies to complement alternative pathway proteins (Factor I, Factor B, C3 and Properdin) were found. Functional assays showed that these autoantibodies cause alternative pathway activation.

Conclusion: This case is the first reported of a heterozygous C3 mutation associated with lupus nephritis and autoantibodies against complement alternative pathway proteins (Factor I, Factor B, C3 and Properdin).These autoantibodies cause activation of this pathway and this fact could explain that the tissue damage is restricted to the kidney.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autoantibodies / immunology*
  • Complement C3 / genetics*
  • Complement C3 / immunology
  • Complement Factor B / immunology
  • Female
  • Fibrinogen / immunology
  • Heterozygote
  • Humans
  • Kidney / pathology*
  • Lupus Nephritis / genetics*
  • Lupus Nephritis / immunology
  • Lupus Nephritis / pathology
  • Mutation
  • Properdin / immunology
  • Young Adult

Substances

  • Autoantibodies
  • Complement C3
  • Properdin
  • Fibrinogen
  • Complement Factor B