Last reviewed 03/2021

The cause is unknown. It is thought to be multifactorial involving genetic and environmental elements with female sex strongly influencing pathogenesis (1,2).

Recognised genetic and epidemiological predisposing factors include:

  • hereditary:
    • the concordance for identical twins is 30% compared to 5% for other sibs
  • complement deficiencies:
    • the strongest disease susceptibility genes are those associated with homozygous complement deficiencies (C1q, C1r, C1s, C2 and C4)
  • female sex
    • female hormones are thought to play an important role although the mechanism is unclear (3)
  • associated with HLA-DR2, HLA-DR3 and C4A null complement alleles
  • a particular MHC haplotype that is commonly found in caucasian patients with SLE is (HLA-A1, HLA-B8, HLA-DR3, C4AQ*O); this is often a marker of a subset of the disease that is associated with anti-Ro antibodies
  • drugs e.g. hydralazine, procainamide or griseofulvin
  • environmental influences
    • Epstein–Barr virus (EBV) infection
    • ultraviolet light (associated with the presence of the anti-Ro antibody) (4)


  • lupus flares can be caused by different precipitants at different time in the same patient (1).