MSK - Juvenile idiopathic arthritis

Question 1

Definition

Answer 1

Juvenile idiopathic arthritis (JIA) is a group of chronic inflammatory arthritides of unknown cause, affecting children under the age of 16.

Question 2

Types of JIA

Answer 2

• Oligoarticular JIA
• Polyarticular JIA (RH-factor negative)
• Polyarticular JIA (RH-factor positive)
• Enthesitis-related arthritis
• Psoriatic JIA
• Systemic JIA (formely Still’s disease)
• Undifferentiated JIA

Question 3

Oligoarticular JIA

Answer 3

• Most common type (50% of JIA)
• Mildest form (affects 4 or fewer joints)
• Commonly affected joints include knees and ankles
• Associated with chronic uveitis

Question 4

Polyarticular JIA (rheumatoid factor-negative)

Answer 4

• Next most common type
• Affects 5 (+) joints in the first 5 months
• Similar joints affected to those in rheumatoid arthritis
• Rheumatoid factor negative
• Some association with chronic uveitis

Question 5

Polyarticular JIA (rheumatoid factor-positive)

Answer 5

• Occurs in pre-teen and adolescent females.
• Affects 5 or more joints in the first 5 months
• Similar joints affected to those in rheumatoid arthritis
• Rheumatoid factor positive

Question 6

Enthesitis-related arthritis

Answer 6

• Arthritis, occurring in the hips, knees, ankles and feet
• Enthesitis (inflammation of the insertion of the ligament or tendon to the bone), occurring in the knees, heels and plantar region of the feet
• More common in boys, unlike other JIA types
• Associated with acute anterior uveitis

Question 7

Psoriatic JIA

Answer 7

Associated with psoriasis, which usually precedes the arthritis but may occur years later.

Question 8

Systemic JIA (formerly Still’s disease)

Answer 8

• Arthritis is preceded by a fever and rash
• Classical “salmon-pink” rash
• In severe forms, inflammation can affect the spleen, liver, pleura and pericardium
  Affects males and females equally

Question 9

Undifferentiated JIA

Answer 9

• Clinical features do not fit into any of the above categories
• Clinical features may fit into multiple categories

Question 10

Epidemiology

Answer 10

• JIA = MC chronic rheumatic disease in children.
• Female predominance : in most subtypes, except for enthesitis-related arthritis
• Genetic predisposition: HLA associations vary by subtype
• Possible triggers:
  = infections,
  = environmental factors

Question 11

Signs

Answer 11

• Joint swelling
• Joint warmth
• Limited range of movement in affected joints
• Limited (if lower limb joints are affected)
• Salmon-pink rash (Systemic JIA only):
  = discrete
  = macules of different sizes
  = occurs with a rash which migrates across the trunk and proximal extremities

Question 12

Symptoms

Answer 12

• Joint pain
• Joint stiffness (in the morning)
• Fatigue
• Fatigue (systemic JIA only)

Question 13

Diagnosis

Answer 13

• ESR/CRP: elevated (esp systemic JIA)
• Rheumatoid factor: type of PA JIA
• HLA B27: assosciated with undifferentiated, enthesitis-related + psoriatic JIA types
• Joint X-ray: joint space narrowing, erosions + bony ankylosis
• Joint USS: visualise joint effusions, synovial thickening + bone erosions

Question 14

Treatment FIRST LINE

Answer 14

• Intra-articular corticosteroids: all patients + 3-6 monthly assessment
• IV corticosteroids: Short-term use = control severe symptoms or in cases of systemic JIA
• METHOTREXATE: DMARD = slow disease progression and prevent joint damage.
  = Avoided if presence of sacro-ilitis or macrophage activation syndrome (MAS).
• NSAIDs: IBUPROFEN used to reduce inflammation and alleviate pain
• Physiotherapy and occupational therapy

Question 15

Treatment SECOND LINE

Answer 15

• Etanercept: Anti-TNF antibody = first biological agent choice,
  = unless presence of sacro-ilitis or macrophage activation syndrome (MAS)
  = Should be avoided in those with uveitis.
• Anakinra: Interleukin-1 (IL-1) receptor antagonist is offered to those with macrophage activation syndrome.
• Tocilizumab: Anti-interleukin-6 receptor antibody is offered to those with systemic JIA (Still’s disease) or those who have not tolerated anakinra.

Question 16

Complications

Answer 16

• Joint deformities and functional disability
• Growth disturbances
• Uveitis
• Osteoporosis
• Secondary amyloidosis: with systemic JIA only
• Pericarditis, pleuritis, peritonitis: with systemic JIA only
• Macrophage activation syndrome (MAS)

Question 17

Macrophage activation syndrome (MAS)

Answer 17

A life-threatening condition seen in 10% of JIA cases, caused by uncontrolled activation and proliferation of T lymphocytes and macrophages. It presents as a sepsis-like condition:
- fever,
- hepatosplenomegaly
- haemorrhagic manifestations.