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Systemic lupus erythematosis (SLE): Etiology and pathogenesis



Systemic lupus erythematosis is a classic prototype of non-organ specific autoimmune disease
Systemic lupus erythematosis is a classic prototype of non-organ specific autoimmune disease characterized by a bewildering array of auto-antibodies particularly antinuclear antibodies (ANAS). It is a chronic remitting and relapsing often-febrile illness characterized principally by injury to the skin, joints, kidney and serosal membranes. Each and every part of the body may be affected. It is common among women of child bearing age and a female to male ratio of 9:1, pick on set 2nd to 4th decade

 Etiology and pathogenesis

The fundamental defect in SLE is a failure of regulatory mechanism that sustains self-tolerance. The cause of SLE remains unknown but it appears to be a complex disorder of multi-factorial origin resulting from interactions including:

1. Genetic factors

Increased familial risk, 24% concordance in monozygotic twins (1-3 in dizygotic) defects in early complement components (C2 or C4) etc. MHC regulates production of specific auto-antibodies

2. Hormonal factors

Estrogens confer increased risks (10 times more common in females than males) that accelerate during pregnancy and menses. Androgens however, confer decreased risk



3. Environmental factors

Drugs such as hydralazine, pencillinetc induce SLE – like illness ) in which all acting in concert to cause activation of helper T-cells and B-cells that results in the secretion of several species of autoantibodies.
·        Ultraviolet rays
·        Emotional stress
·        Surgery

4. Immunologic factors

         I. B cell hyperactivity with hyper gammaglobulinemiaI
    
     II .  Auto-antibodies present with reactivity to DNA, RNA, or phospholipids thus, antinuclear anti bodies (ANA) are the ones that are directed against several nuclear antigen grouped into four categories
1. Antibodies to DNA
2. Antibodies to history
3. Antibodies to non-histone proteins bound to RNA
4. Antibodies to nucleolar antigens
ANAs is virtually positive in every patient with SLE i.e sensitive but it is not specific (other autoimmunity positivity. Regardless of the exact sequence by which auto-antibodies are formed, they are clearly the mediators of tissue injury.

Type III hypersensitivity reaction is responsible for most visceral lesions. 
DNA – anti – DNAcomplexes can be detected in the glomeruli and small blood vessels. Autoantibodiesagainst red cells, white cells and platelets mediate their effects via type II hypersensitivity.

In tissues, nuclei of damaged cells react with ANAs, lose their chromatin pattern, and become homogenous to produce so – called lupus erythematous (LE) bodies or hematoxylin bodies. Related to this phenomenon is the LE cell, which is readily seen, in vitro.Basically, the LE cell may phagocyte leukocytes (neutrophiles or macrophages) that has engulfed the denatured nucleus of an injured cell.

Serum complement levels often decreased due to immune mediated compliment consumption. It is mostly IgG type, lesser extent of the IgM type

Clinicopathologic features

Typically the patients’ young woman with a butterfly rash over the face. Generally the course of the disease is varible and almost unpredictable. ANAs can be found in virtually 100% of patients but, not specific. The detection of antibodies against double stranded DNA and Sm antigen are virtually diagnostic of SLE
Chronic discoid lupus erythmatosis is a disease where its skin involvement may mimic SLE. SLE may affect almost any organ system in variable combinations; this vast heterogenicity in clinical presentation requires a clinical index of suspicion followed by laboratory confirmation. Thus, criteria for the diagnosis of SLE are coined such as molar rash, photosensitivity, oral ulcer, arthritis, renal disorders, hematological disorder, immunologic disorder and antinuclear antibody.

A person is said to have SLE in any four or more of the criteria are present serially or simultaneously. Morphologic changes in SLE are also extremely variable. The most characteristic lesions result from the deposition of immune complexes found in the blood vessels, kidneys, connective tissue and skin. Acute necrotizing vasculitis of small arteries and arterioles is characterized by fibrinoid necrosis.
Kidney: 60 – 70% involvement by SLE. Anti–dsDNA (60-90%associated with nephritis
Skin: Acute lesions “butterfly” rash (50%) where histology shows liqufactive degeneration of the basal layer of the epidermis. Sunlight exposure incites or accentuates the erythema. 



Chronic lesion: Descoid(plaques with scales, scarring with central atrophy)

Joints: Arthralgia or non-erosive synovitis (unlike rheumatoid arthritis) with little deformity

CNS: Neuropsycatric manifestations including seizures, (focal or generalized), psychosis and organic brain syndrome.
Serositis - Acute, subacute or chronic inflammations of the serosal linings pluritis (30-60%), pericarditis (20-30%), peritonitis (60%)
CVS - Myocarditis leading to arrhythmias, congestive heart failures etc. Non-bacterial varrucous endocarditis (Libbman sacks endocarditis) is a warty deposition of valvularwalls. Accelerated coronary atherosclerosis with evidence of angina pectoris and myocardial infection.
Spleen - is moderately enlarged with focal hyperplasia
Lungs -Pleuritis and pleural effusion are the most common pulmonary manifestations.
Systemic lupus erythematosis (SLE): Etiology and pathogenesis Systemic lupus erythematosis (SLE): Etiology and pathogenesis Reviewed by gafacom on November 08, 2019 Rating: 5

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