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Musculoskeletal > Rheumatoid arthritis > Flashcards

Rheumatoid arthritis Flashcards

1
Q

Rheumatoid arthritis

A

Chronic autoimmune disease characterised by pain, stiffness and symmetrical synovitis (inflammation of the synovial membrane) of synovial (diarthrodial) joints
-synovial joints=free moving joints

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2
Q

Key features of rheumatoid arthritis

A

CHRONIC ARTHRITIS
-polyarthritis (>5 joints affected)
-common swelling of small joints of hand and wrists
-symmetrical
-early morning stiffness in and around joints (lasts several hours)
-may lead to joint damage and destruction=’joint erosions’ on radiographs=impaired quality of life
EXTRA-ARTICULAR DISEASE CAN OCCUR=rheumatoid arthritis is a systemic inflammatory disease so other organ involvement
-rheumatoid nodules (subcutaneous)
-others rare eg: vasculitis, episcleritis
RHEUMATOID FACTOR DETECTED IN BLOOD
-IgM autoantibody in blood against IgG=important diagnostically

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3
Q

Rheumatoid arthritis epidemiology

A
  • 1% of population affected
  • affects younger to middle aged patients=common cause of significant disability in young adults
  • female to male ratio=3:1 (effect of female hormones in immune system?)
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4
Q

Rheumatoid arthritis genetic component

A

-specific HLA-DRB gene variants mapping to amino acids 70-74 of DRbeta chain=strong association with rheumatoid arthritis

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5
Q

Rheumatoid arthritis environmental component

A

-smoking= contributes 25% of population-attributable risk and interacts with shared epitope to increase risk

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6
Q

Commonest affected joints in rheumatoid arthritis

A
  • Metacarpophalangeal joints (MCP)
  • Proximal interphalangeal joints (PIP)
  • Wrists
  • Knees
  • Ankles
  • Metatarsophalangeal joints (MTP)

EARLY DISEASE IN HANDS AND FEET

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7
Q

Swan-neck deformity of rheumatoid arthritis

A
  • affects ring finger

- hyperextension at PIP joint and hyperflexion at DIP joint

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8
Q

Boutonniere deformity of rheumatoid arthritis

A
  • affects little finger

- hyperflexion at PIP joint

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9
Q

Radiograph joint damage and destruction of rheumatoid arthritis

A
  • almost appears like dislocation
  • classical bilateral ulnar deviation of fingers
  • observe symmetrical involvement of joints
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10
Q

Extra rheumatoid arthritis pathology

A

PRIMARY PATHOLOGY SITE IS IN SYNOVIUM LOCATED AT:

  • synovial joints=PIP synovitis (soft on palpation)
  • tenosynovium surrounding tendons=extensor tenosynovitis (swelling not above wrist or MCP joints, patient has incomplete extension of little and ring fingers=consistent with extensor tendon damage by tenosynovitis)
  • bursa=olecranon bursitis example
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11
Q

Subcutaneous nodules in rheumatoid arthritis

A
  • classically occur slightly distal to elbow (ulnar border of forearm)
  • central core of fibrinoid necrosis surrounded by histocytes and peripheral layer of connective tissue
  • occurs in ~30% of patients
  • associated with severe disease, extra-articular manifestations and rheumatoid factor
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12
Q

Rheumatoid factor

A

IgM anti-IgG antibodies

  • antibodies recognise Fc portion of IgG as their target antigen
  • positive in 70% at disease onset and further 10-15% become positive over first 2 years of diagnosis
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13
Q

Early rheumatoid arthritis radiographic abnormalities

A

Juxta-articular osteopenia (darker/more translucent on x-ray)

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14
Q

Later rheumatoid arthritis radiographic abnormalities

A

Joint erosions at margins of joint (‘nibble’ out of joint edge)

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15
Q

Very late rheumatoid arthritis radiographic abnormalities

A

Joint deformity and destruction

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16
Q

Synovial joint contents

A

SYNOVIUM
-1 to 3 cell deep lining
-contains type A synoviocytes (phagocytic), type B synoviocytes ( fibroblast like producing hyaluronic acid) and type I collagen
SYNOVIAL FLUID
-hyaluronic acid-rich viscous fluid
ARTICULAR CARTILAGE
-type II collagen and proteoglycan (mainly aggrecan)

17
Q

Synovial membrane in rheumatoid arthritis

A

-synovium becomes proliferated mass of tissue (pannus) due to neovascularisation, lymphangiogenesis, inflammatory cells (B/T lymphocytes, plasma cells, mast cells and activated macrophages)

18
Q

Symmetrical polyarthritis

A
  • symmetrical pattern

- often find callous formation under metatarsal heads due to joint deformity

19
Q

Antibodies to citrullinated protein antigens

A
  • ANTI-CYCLIC CITRULLINATED PEPTIDE ANTIBODIES=highly specific antibodies for rheumatoid arthritis
  • citrullination of peptides is mediated by enzyme peptidyl arginine deiminases (PADs)=convert arginine to citrulline
  • PADs present in high concentrations in neutrophils and monocytes so increased citrullination of autologous peptides in inflamed synovium (more active at sites of inflammation)
  • ACPA strongly associated with smoking and HLA shared epitope
  • shared epitope preferentially binds non-polar amino acids like citrulline but not positively charged amino acids like arginine=ACPA more likely to develop among individuals with citrullinated autoantigens who have shared epitope
  • smoking increases ACPA-positive rheumatoid arthritis risk=more citrullination in lungs
20
Q

ACPA and rheumatoid arthritis

A
  • individual susceptible if carrying shared epitope (conserved amino acid sequence in HLA-DR antigen-binding groove)=shared sequence in amino acids 70-74 of HLA-DRbeta chain
  • hence, multiple different HLA serotypes are associated with disease=all have shared epitope
  • shared epiptope preferentially binds non-polar amino acids (citrulline) and citrulline-containing peptide antigens increased during inflammation
  • environmental factors can result in inflammation increasing citrullination (smoking, changes in microbiota, chronic infections such as gingivitis)=cause of anti-CCP antibody development in rheumatoid arthritis being genetic factor and environmental factor combination
21
Q

Extra-articular features of rheumatoid arthritis

A 
COMMON
-fever
-weight loss
-subcutaneous nodules
UNCOMMON
-vasculitis
-ocular inflammation eg: episcleritis
-neuropathies
-amyloidosis
-lung disease (nodules, fibrosis and pleuritis)
-felty's syndrome (triad of splenomegaly, leukopenia and rheumatoid arthritis)

Musculoskeletal (8 decks)

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