Rheumatoid Arthritis Flashcards
At what age is the peak prevalence of RA?
30-50 years
What is rheumatoid arthritis?
A chronic systemic autoimmune disorder causing a symmetrical polyarthritis
Describe the aetiological role of gender in RA?
Women before the menopause are affected 3x more often than men. After menopause there is an equal sex incidence, suggesting an aetiological role for sex hormones
What antigens confer susceptibility to RA?
HLA-DR4 and HLA-DRB1*0404/0401. This human leukocyte antigens are associated with more severe disease
What is rheumatoid factor? How often is it present in patients with RA?
Rheumatoid factor is autoantibodies directed against the Fc portion of immunoglobulin. These autoantibodies are produced by B cells. It is positive in 70% of patients. It is not, however, specific for RA and occurs in connective tissue disease and some infections
What is citrullination?
The conversion of the amino acid arginine in a protein into the amino acid citrulline. The immune system often attacks citrullinated proteins, leading to autoimmune diseases such as rheumatoid arthritis
What is anti-CCP?
Anti-CCP (anti- cyclic citrullinated peptides) are autoantibodies that are directed against peptides and proteins that are citrullinated. Anti-CCP (also known as ACPA (anti-cirullinated protein antigen) is often present in patients with rheumatoid arthiritis.
What antibody class is most rheumatoid factor?
IgM
Why are anti-CCP antibodies important markers for diagnosis and prognosis of RA?
- They are as sensitive and more specific than IgM RF
- They may predict eventual development into RA when found in undifferentiated arthritis
- They are a marker of erosive disease in RA
- They may be detected in healthy individuals years before onset of clinical RA
- Anti-CCP rarely occurs in healthy people (while healthy people can also have RF)
- Combination of RF and anti-CCP positive results makes RA very likely
- These seropositive patients have a poorer prognosis and often need more aggressive treatment
What is the importance of TNF in RA?
Overproduction and overexpression of tumour necrosis factors is a key inflammatory element in RA, leading to synovitis and joint destruction. TNF-α stimulations overproduction of IL-6. Antibodies to TNF-α and IL-6 produce marked short-term improvements in synovitis demonstration the role of these cytokines in RA
What are the characteristic pathological features of RA?
- Synovitis (inflammation of the synovial lining of joints, tendon sheaths or bursae)
- Thickening of the syovial lining
- Infiltration of the synovial lining by inflammatory cells
Describe the normal synovium
Thin, comprising a lining layer a few cells thick containing fibroblast-like synoviocytes and macrophages overlying loose connective tissue
How do angiogenic cytokines contribute to the development of RA?
They induce generation of new synovial blood vessels
How do activated endothelial cells contribute to the development of RA?
They produce adhesion molecuels such as vascular cell adhesion molecule-1 (VCAM-1) which expedite extravasation of leucocytes into the synovium
What is a pannus?
Proliferation of the synovium causes it to grow out onto the cartilage surface producing a tumour like mass called a pannus.
Why is the development of a pannus damaging to the joint?
The pannus damages the underlying cartilage by blocking its normal route for nutrition and by the direct effects of cytokines on the chondrocytes. The cartilage then becomes thinned, exposing the underlying bone, producing the diagnostic juxta-articular bony ‘erosions’ seen on X-ray
What early damage is caused by fibroblasts in the first 3-6 months of RA?
Fibroblasts from the proleferating synovium grow along the course of blood vessels between the synovial margines and the epiphyseal bone cavity and damage the bone. This early damage justifies the use of DMARDs within 3-6 months of onset of arthritis
What is seronegative RA? How is it diagnosed?
The term ‘seronegative RA’ is used for patients in whom the standard tests for IgM rheumatoid factor are per- sistently negative. They tend to have a more limited pattern of synovitis.
Diagnosis is made based on symptoms and signs and confirmed by ultrasound of joints showing synovitis
What is the difference between seropositive and seronegative RA in terms of Hb and inflammatory markers?
In seropositive RA, inflammatory markers are high and Hb may be low
In seronegative RA inflammatory markers are lower and Hb is normal
IgM RF is neither diagnostic of RA, nor does its absence rule disease out. Why then is it still a useful test?
It is a useful predictor of prognosis. A persistently high titre in early disease implies more persistently active synovitis, more joint damage and great disability eventually, and justifies earlier use of DMARDs
What is the most typical presentation of RA, occuring in approx. 70% of cases?
A slowly progressive, symmetrical peripheral polyarthritis, evolving over a period of a few weeks or months
How does RA present less commonly, in approx 15% of cases?
Rapid onset occuring over a few days (or explosively overnight) with a severe symmetrical polyarticular involvement, especially in the elderly.
What factors indicate poor prognosis?
- Older age
- Female sex
- Symmetrical small joint involvement
- Morning stiffness lasting >30 mins
- > 4 swollen joints
- CRP >20
- Positive RF and ACPA
What are the differentials for early signs of RA?
- Post viral arthritis: rubella, hep. B or erythrovirus
- Seronegative spondyloarthopathies
- Polymyalgia rheumatica
- Acute nodal osteoarthritis (PIPs and DIPs involved)