Systemic autoimmune condition that mainly involves the skin, joints, kidneys, blood cells, and nervous system but can affect almost any organ system

Aetiology

• Autoimmune
  • Genetic predisposition - HLA genes
  • Hormonal factors - ↑ oestrogen
  • Environmental factors - UV light, bacterial/viral infection, some medications

Risk factors

• Higher prevalence in women (9:1)
  • Usually presents in childbearing years - 20-40
• More common and more severe in those of Afro-Caribbean, Hispanic American, Asian, and Chinese ethnicity

Pathophysiology

• Immune system attacks cells and tissues resulting in inflammation and tissue damage, also involves the formation of immune complexes (type III hypersensitivity)

1. Loss of immune regulation results in increased and defective apoptosis
2. Necrotic cells release nuclear materials which act as auto-antigens
3. Auto-immunity results from exposure to nuclear and cellular auto-antigens
4. B and T cells stimulated and autoantibodies are produced
5. Auto-antigens and autoantibodies form immune complexes which circulate and become deposited in the basement membrane (type III hypersensitivity)
6. Activation of complement which attracts leukocytes which release cytokines
7. Cytokine release perpetuates inflammation which causes necrosis and scarring

Lupus nephritis

• Up to 50% of lupus patients will have renal involvement at presentation, and up to 60% during the course of their disease
• Most frequently observed abnormality is proteinuria