Pathology of Systemic Lupus Erythematosus
Systemic lupus erythematosus (SLE) is a chronic disease with many manifestations. SLE is an autoimmune disease in which the body's own immune system is directed against the body's own tissues. The etiology of SLE is not known. It can occur at all ages, but is more common in young women. The production of autoantibodies leads to immune complex formation. The immune complex deposition in many tissues leads to the manifestations of the disease. Immune complexes can be deposited in glomeruli, skin, lungs, synovium, mesothelium, and other places. Many SLE patients develop renal complications.
The presence of autoantibodies can usually be determined by the antinuclear antibody (ANA) test performed on patient serum from blood. The titer, or strength, of the ANA gives a rough indication of the severity of the disease. Not all positive ANA tests indicate autoimmune disease, particularly when the titer is low. After a positive screening ANA test, more specific tests for SLE include detection of auto-antibodies to double stranded DNA and to Smith antigen.
Skin rashes are common with SLE. The most characteristic rash is seen across the malar region of the face, the so-called "butterfly rash" that is accentuated by sun exposure. SLE must be distinguished from discoid lupus erythematosus (DLE) which affects the skin (but only in sun exposed regions) and is unlikely to be associated with systemic illness, such as renal disease. A biopsy of sun exposed skin that is not involved with a rash will demonstrate immune complex deposition with SLE, but not with DLE.
Renal disease is common with SLE because the immune complexes are often deposited in the renal glomeruli. A renal biopsy is often performed to determine the degree of involvement and determine therapy. Despite therapy, progression to chronic renal failure is common.
Immune complex deposition in mesothelium can potentiate formation of effusions in body cavities. Besides pericardial effusions and serous pericarditis, SLE patients can have a form of endocarditis called Libman- Sacks endocarditis. Synovial immune complexes can lead to arthralgias.