Systemic lupus erythematosus is an autoimmune rheumatic disorder that can present with symptoms in almost any organ or system of the body. It is 10 times commoner in women than men, and commoner in Afro-Caribbeans than in other ethnic groups. Its aetiology is multifactorial, incorporating genetic, hormonal, and environmental elements. No single abnormality of the immune system can be considered responsible, pathogenesis depending on the interplay of several different factors, including autoantibodies, T lymphocytes, cytokines, the complement system, and apoptosis. Common symptoms are constitutional (fatigue, anorexia), musculoskeletal (arthralgia/arthritis, myalgia), dermatological (alopecia, butterfly rash, vasculitic skin lesions, purpura), cardiopulmonary (breathlessness, pleurisy), and neurological (migraine, seizures, depression, psychosis). Treatment for mild disease is NSAID, analgesics and hydroxychloroquine, more severe disease requires corticosteroid and immunosuppressant drugs.