Pathology - Systemic Lupus Erythematosus (SLE)

Pathology - Systemic Lupus Erythematosus (SLE)
I. Definition & Epidemiology:

Definition: SLE is a multisystem autoimmune disease characterized by the production of autoantibodies targeting nuclear and cytoplasmic antigens. This means the body's immune system mistakenly attacks its own cells.
Epidemiology:

II. Etiology & Pathogenesis:

Etiology (Cause): Unknown. A leading hypothesis suggests defective phagocytosis (the process of engulfing and destroying pathogens) of apoptotic bodies (dying cells). This failure to properly clear apoptotic cells exposes intracellular self-antigens, potentially triggering an autoimmune response.
Pathogenesis (Mechanism):

Autoreactive B and T cells (immune cells) become activated.
Immune complexes form: Autoantibodies bind to self-antigens.
These circulating immune complexes deposit in various tissues (skin, joints, kidneys).
Tissue inflammation and damage result from the immune complex deposition. (Visualize this process using Fig 18.1 if available).

III. Clinical Presentation (Symptoms):
SLE's wide-ranging symptoms depend on the affected organs. Remember the diverse nature of its presentations:

Common Symptoms: Fatigue, weight loss, low-grade fever.
Musculoskeletal: Arthralgia (joint pain).
Skin: Scaly red lesions (often on sun-exposed areas).
Pulmonary: Pleuritis (lung inflammation), pleural effusion (fluid buildup around lungs), pneumonitis (lung inflammation), potentially leading to pulmonary fibrosis (scarring).
Renal: Glomerulonephritis (kidney inflammation), leading to chronic kidney disease. This is a serious complication.
Hematological: Anemia (low red blood cell count), lymphopenia (low lymphocyte count), thrombocytopenia (low platelet count).

IV. Immunology (Diagnostic Markers):
Specific autoantibodies are key diagnostic indicators. Note the high prevalence of certain markers:

Anti-nuclear antibodies (ANA): >95% of SLE patients test positive. This is a common, but non-specific, finding.
Anti-double-stranded DNA (dsDNA) antibodies: 60% of patients. More specific to SLE.
Anti-Smith antigen antibodies: 20-30% of patients. Very specific to SLE.
Anti-phospholipid antibodies: 20-30% of patients. These antibodies cause a hypercoagulable state (increased risk of blood clots).

V. Prognosis:

15-year survival rate: Approximately 80% from the time of diagnosis.
Causes of death: Often related to severe renal (kidney) and pulmonary (lung) complications.

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