Rheumatoid arthritis is a chronic autoimmune disease that primarily attacks the joints, causing inflammation of the synovium and destruction of articular cartilage and bone. It peaks in the second to fourth decades and is more common in women. Systemic manifestations can include hematologic, pulmonary, neurological and cardiovascular abnormalities. While its exact cause is unknown, it is believed to involve a combination of genetic, environmental and immunological factors. The characteristic pathology involves proliferative synovitis, pannus formation, and erosion of cartilage and bone in the joints. Extra-articular manifestations can include rheumatoid nodules in the skin and internal organs. Variants include juvenile rheumatoid arthritis and Felty's syndrome.

1. Mrs. Rishita D Patel

2.  Rheumatoid arthritis (RA) is a chronic inflammatory disorder of
autoimmune origin that may affect many tissues and organs but
principally attacks the joints,
producing a nonsuppurative proliferative and inflammatory synovitis.
 RA often progresses to destruction of the articular cartilage and ankylosis
of the joints.

3.  Extraarticular lesions may involve skin, heart, blood vessels and lungs.
 The prevalence in the United States is approximately 1%.
 In India, estimated prevalence rate of RA is 0.5%–0.75%.[25-Aug-2020]
 The disease peaks in the second to fourth decades and is three times more
common in women than men.

4.  systemic manifestations include haematologic, pulmonary, neurological and
cardiovascular abnormalities.
 ETIOPATHOGENESIS
On based on etiology and pathogenesis proposes that RA occurs in an immunogenetically
predisposed individual
to the effect of microbial agents acting as trigger antigen.
The role of superantigens which are produced by several microorganisms with capacity to
bind to susceptible gene [HLA-DR molecules (MHC-II region)] has also emerged.

5.  A number of observations in research indicates the role of immune processes,
particularly autoimmune phenomenon, in the development of RA. These include the
following:
1. Detection of circulating autoantibody called rheumatoid factor (RF) against Fc
portion of autologous IgG in about 80% cases of RA.
RF antibodies are heterogeneous and consist of IgM and IgG class.
2. The presence of antigen-antibody complexes (IgG-RF complexes) in the circulation as
well as in the synovial fluid.
3. The presence of other autoantibodies such as antinuclear factor (ANF), antibodies
to collagen type II, and antibodies to cytoskeleton.

6. 4. Antigenicity of proteoglycans of human articular cartilage.
5. The presence of g-globulin, particularly IgG and IgM, in the synovial fluid.
6. Association of RA with amyloidosis.
7. Activation of cell-mediated immunity as observed by presence of numerous
inflammatory cells in the synovium, chiefly CD4+ T lymphocytes and some
macrophages.

7.  Though the above hypothesis of a possible role of autoimmunity in the etiology and
pathogenesis of RA is generally widely accepted, controversy continues as regards the
trigger events which initiate the destruction of articular cartilage. Various
possibilities which have been suggested are as follows:
1. The existence of an infectious agent such as mycoplasma, Epstein-Barr virus
(EBV), cytomegalovirus (CMV) or rubella virus, either locally in the synovial
fluid or systemic infection some time prior to the attack of RA.
1. The possible role of HLA-DR4 and HLA-DR1 in initiation of immunologic damage.

8. i) In response to antigenic exposure (e.g. infectious agent) in a genetically
predisposed individual (HLA-DR), CD4+ T-cells are activated.
ii) These cells elaborate cytokines, the important ones being tumour necrosis
factor (TNF)-a, interferon (IF)-g, interleukin (IL)-1 and IL-6.
iii) These cytokines activate endothelial cells, B lymphocytes and macrophages.
iv) Activation of B-cells releases IgM antibody against IgG (i.e. anti-IgG); this
molecule is termed rheumatoid factor (RF).

9. v) IgG and IgM immune complexes trigger inflammatory damage to the synovium,
small blood vessels and collagen.
vi) Activated endothelial cells express adhesion molecules which stimulate collection
of inflammatory cells.
vii)Activation of macrophages releases more cytokines which cause damage to joint
tissues and vascularisation of cartilage termed pannus formation.
viii)Eventually damage and destruction of bone and cartilage are followed by fibrosis
and ankylosis producing joint deformities.

11.  The predominant pathologic lesions are found in the joints and tendons, and less often,
extra-articular lesions are encountered.
 ARTICULAR LESIONS
RA involves first the small joints of hands and feet and then symmetrically affects the
joints of wrists, elbows, ankles and knees.
The proximal interphalangeal and metacarpophalangeal joints are affected most
severely.
Frequently cervical spine is involved but lumbar spine is spared

13.  The characteristic feature is diffuse proliferative synovitis with formation of pannus.
The microscopic changes are as under
1. Numerous folds of large villi of synovium.
2. Marked thickening of the synovial membrane due to oedema, congestion and
multilayering of synoviocytes.
3. Intense inflammatory cell infiltrate in the synovial membrane with predominance of
lymphocytes, plasma cells and some macrophages, at places forming lymphoid
follicles.
4. Foci of fibrinoid necrosis and fibrin deposition.

14.  The pannus progressively destroys the underlying cartilage and subchondral bone.
 This invasion of pannus results in demineralisation and cystic resorption of
underlying bone.
 Later, fibrous adhesions or even bony ankylosis may unite the two opposing joint
surfaces.
 In addition, persistent inflammation causes weakening and even rupture of the
tendons.

16.  Nonspecific inflammatory changes are seen in the blood vessels (acute vasculitis),
lungs, pleura, pericardium, myocardium, lymph nodes, peripheral nerves and eyes.
 But one of the characteristic extra-articular manifestation of RA is occurrence of
rheumatoid nodules in the skin.
 Rheumatoid nodules are particularly found in the subcutaneous tissue over pressure
points such as the elbows, occiput and sacrum.
 Similar nodules may be found in the lung parenchyma, pleura, heart valves,
myocardium and other internal organs.

20. 1. Juvenile RA found in adolescent patients under 16 years of age is characterised by
acute onset of fever and predominant involvement of knees and ankles. Pathologic
changes are similar but RF is rarely present.
1. Felty’s syndrome consists of polyarticular RA associated with splenomegaly and
hypersplenism and consequent haematologic derangements.
2. Ankylosing spondylitis or rheumatoid spondylitis is rheumatoid involvement of the
spine, particularly sacroiliac joints, in young male patients. The condition has a
strong HLA-B27 association and may have associated inflammatory diseases such
as inflammatory bowel disease, anterior uveitis and Reiter’s syndrome.