SYSTEMIC LUPUS ERYTHEMATOSUS: PATHOGENESIS, CLINICAL FEATURES, HISTOPATHOLOGY AND TREATMENT
Author: Sanketh DS, MDS
Systemic lupus erythematosus (SLE) is a multi-factorial, auto-immune and multi-systemic disease characterised by formation of auto-antibodies and immune complexes which damage various tissues and organs resulting in a wide variety of clinical manifestions.
ETIOLOGY & PATHOGENESIS
SLE is an auto-immune disorder, where the immune cells attack the body’s own cells. Before we go into the details of the hypothetic model explaining the pathogenesis of this disorder, let us try to understand what may trigger the disease. This happens primarily due to 3 etiological factors namely, a) genetic b) environmental and c) immunological factors.
Some people may inherit certain genes making them susceptible to develop the disorder. For example
1. Certain MHC genes help in production of auto-antibodies.
2. Some patients may genetically inherit deficiencies in certain complement proteins, which may impair clearance of immune complexes and apoptotic bodies.
Several environmental factors like Ultra Violet (UV) light, viruses like Ebstein Barr virus, drugs like hydralazine, procainamide and penicillamine and sex hormones like estrogen may trigger the disorder by inducing apoptosis of healthy cells.
The most important immunological aberration is the defect in eliminating self-reacting B and T cells, that is B and T cells that recognise self-antigens and attack the body’s own cells, tissues and organs.
HYPOTHESIS – PATHOGENESIS OF SLE
Environmental factors may insult cells inducing apoptosis or programmed cell death. Normally, apoptotic bodies are engulfed by phagocytic cells and are cleared before these apoptotic bodies could induce inflammation. However, in SLE patients the ability of these phagocytes to clear apoptotic bodies is defective, allowing them to persist for a longer time. Exposed with the apoptotic bodies are the nuclear antigens of the cell, like DNA, RNA and histones. Nearby dendritic cells may collect these nuclear antigens and present it to self –reacting T cells. T cells are activated which then activate self-reacting B cells to produce auto-antibodies against these nuclear antigens. Since these antibodies are targeted against the nuclear antigens, they are called anti-nuclear antibodies. Anti-nuclear antibodies bind with the nuclear antigens forming immune complexes and get into the blood stream, where they get deposited in the vessel walls. Also, complexes flow with the blood and get deposited in various organs, like kidneys, joints and the skin. Normally immune complexes are cleared by the system so that it does not induce inflammation. However, due to defects in clearance of immune complexes, they may attract complement, induce inflammation and cause damage to the vessel walls and other organs where they are deposited. In addition to this, auto-antibodies are also formed against red blood cells, white blood cells and platelets causing destruction of these cells.
With the wide variety of clinical manifestations, SLE is very difficult to diagnose. Women, especially of child bearing age are 10 times more susceptible to SLE, with the mean age of diagnosis being 31 years. Patients initially manifest with fever, malaise, arthritis, weight loss and fatigue. Patients develop a characteristic erythematous, butterfly-shaped rash that runs over the cheeks and across the bridge of the nose.
Oral manifestations occur in 20-50% of patients and manifest most commonly on the buccal mucosa, palate and gingiva. Oral lesions manifest in the form of erythematous patches, ulcers and keratinized white plaques. Ulcers may develop on the vermillion, especially of the lower lip with crusting and bleeding. Often, there are white keratotic striae that radiate from the margins of these oral lesions. Oral lesions of SLE often resemble leukoplakia and oral lichen planus.
Organs commonly affected are kidneys and heart. Approximately 40-50% of patients develop complications of the kidney leading to a kidney failure. Cardiac complications like pericarditis affect 50% patients. Also, vegetations composed of fibrin and white blood cells deposit in the valves of the heart causing a type of endocarditis called Libman-Sacks endocarditis.
Apart from the kidneys and the heart, several other organs may also be affected and the criteria for diagnosing SLE was established by American College of Rheumatology (ACR) in 1982 and revised in 1997. The criteria comprises 11 symptoms and a person is diagnosed with SLE if he/she has 4 out of 11 symptoms.
Under the microscope, oral lesions show hyperkeratosis, keratotic plugging, degeneration of the basal layer and a sub-epithelial chronic inflammatory infiltrate that may extend deep into the connective tissue. Perivascular infiltration of lymphocytes may also be observed. Features are similar to oral lichen planus, though it could be differentiated histologically, by the presence of the deeper extension of the inflammatory infiltrate into the stroma and the peri-vascular inflammation.
TREATMENT & PROGNOSIS
Patients should avoid excessive exposure to sunlight in order to prevent triggering of the disease by UV light. Systemic corticosteroids are combined with other immunosuppressive drugs in order to control complications or severe symptoms that involve organs. Oral lesions respond to systemic therapy. Prognosis of the patient depends on the organ involved and the remissions and exacerbations of the disease.
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Systemic Lupus Erythematosus: Pathogenesis and Clinical Features, George Bertsias, Ricard Cervera, Dimitrios T Boumpas.
OTHER (HACKDENTISTRY) PRACTICE/STUDY RESOURCES