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Autoimmune Diseases, ACR(American College of Rheumatology) Diagnostic…
Autoimmune Diseases
What are autoimmune diseases ?Autoimmune diseases are when immune cells attack the self-proteins resulting in tissue damage. Describe the Pathogenesis of autoimmune disease.
- The pathogenesis of autoimmune diseases involves a Genetic Susceptibility plus an Environmental Influence.
- This combination factors results in Defective Antigen Presentation.
- The defective antigen recognition of self antigen as foreign causes a Loss of Tolerance for that self antigen and sets off an inflammatory response.
- When the inflammatory reaction is excessive it is known as Hypersensitivity reactions.
- And if the hypersensitivity reaction causes tissue damage it is known as an autoimmune disease.
How are autoimmune diseases classified ? Autoimmune diseases are classified as as either:
- Systemic: SLE, Rheumatoid Arthritis, Systemic Sclerosis OR
- Organ Specific: Diabetes Mellitus, Myasthenia, Grave's Disease,
Systemic Lupus Erythematosus (SLE)
What is SLE ?
SLE is Systemic Lupus Erythematous a multi systemic auto immune disease.
It is characterized by a vast array of antibodies. Which in turn results in numerous disease manifestations.
What is the Pathogenesis for SLE ? The pathogenesis of SLE involves Genetic Susceptibility and an Environmental Influence, such as Oestrogen and Ultraviolet radiation respectively. These factors/triggers is why:
- SLE is more common in women than men
- Patient will often have a skin (malar) rash.
UV Radiation causes damage with apoptosis of cells
How does the Diagnosis of SLE work ?
Diagnosis of SLE is done through the Antibody Test.
The antibody test to do depends on what autoimmune disease is suspected.
Example:
ANA (AntiNuclear Antibody) is positive in many autoimmune diseases.
It is therefore a sensitive screening marker to test for the initial work up of a patient. To see if a patient has an autoimmune disease.
Anti-dsDNA and Anti-Sm are specific but not sensitive.
They are useful as confirmatory markers to confirm SLE and exclude other autoimmune diseases.
Because SLE patient have numerous antibodies. They can cause a false positive in other serology, eg: VDRL+
VDRL is a test for syphilis.
So a patient who is VDRL positive with a rash do not always have syphilis. It maybe SLE.
Malar (Butterfly), Discoid Rash
How do we distinguish an SLE rash from that of Syphilis ?
The rash in Syphilis involves the palms and soles.
The rash in SLE is a Photosensitive Rash involving the sun exposed area.
Because the cheeks are involved, this malar rash will is also called the Butterfly Rash due to its resemblance of the wings of a butterfly.
Describe the microscopy of the Malar rashMicroscopy (Histology) of Malar Rash:
- Antibodies are deposited along the dermo-epidermal junction of skin.
- With resulting inflammation manifesting into the skin.
What are the causes of death in SLE ? Although, malar rash is the most common symptom of SLE. The causes of death in SLE are as follows:
- Because the pathogenesis of SLE involves the circulation Ag-Ab complexes, these complexes are deposited in the Glomeruli.
Where blood filtration occurs. The Type III Hypersensitivity reaction then causes Glomerulitis, aka Lupus Nephritis. If untreated Renal Failure will follow. NOTE: when managing a patient known with SLE, what would you do to decide the patient's disease progression and response treatment ? Renal Biopsy.
- Intercurrent Infections
- Coronary Artery Disease due to Hyperlipidaemia.
How do we manage SLE ?
- Sunscreen
- Analgesic
- Immune suppression.
SLE is a systemic autoimmune disease. It does not only involve the skin or kidney. It can also involve the Heart Valves.
How does SLE affect the Heart Valves ?
Small-medium vegetation may develop on either on or both sides of the of the valve leaflets.
This is known as Libman-Sacks endocarditis or non-bacterial verrucous endocarditis.
Rheumatoid Arthritis
What is Rheumatoid Arthritis ?
Rheumatoid Arthritis is a chronic multisystem disease characterized by Polyarticular Proliferative Erosive Synovitis.
What is the Pathogenesis of Rheumatoid Arthritis ?
The pathogenesis of Rheumatoid Arthritis is as follows:
Rheumatoid factor (IgM antibody against Fc portion of IgG) associated with disease progression.
The main mechanism of injury in RA involves Cell Mediated Type IV Hypersensitivity Reactions.
Pannus (granulation tissue) causes further erosion.
Environmental Influence: Smoking and the Genetic Susceptibility: Oestrogen
RA occurs in more women that men.
Describe the Joint Pathology(what do you see ?) In Rheumatoid Arthritis
- Hypertrophic Villus Synovitis due to the presence of lymphoid follicles beneath proliferation synovium.
- Pannus is an overgrowth of inflamed granular tissue & fibrosis tissue covering articular surfaces.
- Rice bodies (loose bodies) are which are Fibrin filled with inflammatory cells.
What is a Pannus ?
A pannus is an overgrowth of inflamed granular tissue and fibrosis tissue that cover articular surfaces.
The Pannus start from the periphery where the Synovial Membrane is located.
How does bone and cartilage erosion occur in the Rheumatoid Arthritis ?
The pannus erodes the bone and cartilage causing bone destruction from the periphery inwards.
What happens to joint after the cartilage is completely replaced by Pannus ?
The joint will undergo fibrous and bony ankylosis ( or Joint fusion).
What are the Systemic manifestations of Rheumatoid Arthritis ? Rheumatoid arthritis is not confined to joints and patients may develop systemic manifestations.Systemic Manifestations
- Constitutional Symptoms: Fever, Malaise and Anaemia.
- Rheumatoid Nodule is a subcutaneous nodule with Central Fibrinoid Necrosis and Peripheral Granulomatous Inflammation
- Vasculitis similar to SLE.
- Nodular Scleritis
- Pulmonary Fibrosis
- Felty Syndrome with the combination of Splenomegaly, Neutropaenia, and Rheumatoid Arthritis.
- Caplan Syndrome with the combination of Lung Nodules in mine workers and Rheumatoid Arthritis.
What are the complication of Rheumatoid Arthritis ?Complications are divide into Local, Systemic and Iatrogenic.
- Local Complications:
Carpal Tunnel Syndrome
Subluxation(Antlanto-Axial) , Dislocation
- Systemic Complications:
Amyloidosis
Lymphoma
Other autoimmune diseases (Sjogren)
- Iatrogenic
NSAIDs can cause peptic ulcer.
Steroid can cause infections and osteoporosis
DMARDs can cause nephirits
Management of Prognosis: Analgesia, Immune modulating drugs (DMARDs), Physiotherapy.
What is Systemic Sclerosis ?
Systemic Sclerosis is a systemic autoimmune disease characterized by progressive fibrosis (Fibroblasts activated by T cell cytokines)
Fibrosis does not only involve the skin it can also involve the:
- Vessels cause Malignant Hypertension
- Malignant Hypertension can cause Renal Failure
- Gut causing Malabsorption
- Lung Fibrosis shortness of breath and eventful death.
Other subtypes of Systemic Sclerosis
CREST
Calsinosis
Raynauld Phenomenon
Esophageal dysmotility
Sclerodactyly
Telangiectasia
ACR(American College of Rheumatology) Diagnostic Criteria
Uses 11 Manifestations.
And if patient has 4 or more manifestations he/she is considered to have SLE.
DOPAMIN RASH
Discoid Rash
Oral Ulcer
Photosensitivity
Arthritis
Malar Rash
Immunological (antiSm , Anti-dsDNA, false VDRL+)
Neurological
Renal
ANA
Serositis (pericarditis)
Haematologic