Makindo Medical Notes.com

Aspirin should be avoided in all those under 12 because of the risk of Reye syndrome. Tumour necrosis factor is a proinflammatory cytokine that plays a central role in the pathogenesis of juvenile idiopathic arthritis

About

• It is a systemic form causing 10% of Juvenile Idiopathic arthritis
• Onset early childhood under 16
• A similar form can occur in adults

Aetiology

• Seen most commonly in children under the age of 5
• Onset may be seen at age 2 or even before
• Systemic illness affecting more than just joints.
• M=F but very rarely seen in Adults
• Genetic as shared HLA alleles

Immunology: Imbalance of

• Th1 (IFN-gamma secreting T cells)
• Th17 (interleukin -17 secreting T cells)
• Persistent activation of innate immunity
• Tumour necrosis factor is a proinflammatory cytokine that plays a central role in the pathogenesis of juvenile idiopathic arthritis

Definitions

• Oligoarthritis affects four joints or less during the first six months of disease.
• Polyarthritis: affects five joints or more during the first six months of disease

Subtypes

• a) Oligoarthritis 50-60%
• b) Rheumatoid factor (IgM RF) positive polyarthritis 11-28%
• c) RF negative polyarthritis 2-7%
• d) Systemic arthritis - salmon rash lymphadenopathy, enlarged spleen and liver, serositis
• e) Psoriatic arthritis
• f) Enthesitis-related arthritis 1-6% HLA B27
• g) Undifferentiated arthritis

Clinical: Fever + rash + joint pain

• Arthralgias common in the course of sJIA, but arthritis not always prominent.
• Recurrent fever for more than 2 weeks, rash and painful joints
• A high spiking pyrexia > 39° C usually appearing late evening
• Half develop a destructive arthritis
• A widespread pink or salmon coloured maculopapular rash
• Lymphadenopathy, Myocarditis, Pericarditis and Dry eyes and mouth
• Pleurisy and Hepatosplenomegaly

Investigations

• FBC, U&E, LFT, Raised CRP and ESR
• Markedly elevated concentrations of ferritin an acute inflammatory marker
• Negative autoantibodies usually ANA, RF
• Negative HLA B27 usually
• A positive ANA > 1:100 or Rheumatoid factor > 1:80 excludes the diagnosis
• Raised neutrophils and platelets
• Radiology: no changes early on in the disease
• Ultrasound is capable of assessing synovial thickening, joint effusion, tenosynovitis, enthesitis, and bone erosions.
• Magnetic resonance imaging (MRI) is the gold standard for the study of JIA. All joints involved can be easily examined in all possible plans and with excellent contrast. MRI is the only modality able to objective bone marrow oedema and the most sensitive to detect bone erosions.

Differentials

• Oligoarthritis
  • post-streptococcal reactive arthritis
  • Lyme arthritis
  • Acute rheumatic fever
  • Reactive arthritis
  • Toxic synovitis
  • Septic arthritis
  • Pyomyositis
  • Steroid-induced osteonecrosis
  • Sickle cell disease
  • Haemophilia
  • Scurvy
  • Osteomyelitis
  • Chronic nonbacterial osteomyelitis (CNO)
  • Sport injury
  • Non-accidental injury
  • Pigmented villonodular synovitis (PVNS)
  • Osteoid osteoma,
  • Bone tumour s
  • Neuroblastoma
  • Leukaemia, and lymphoma
• Polyarthritis need to exclude
  • Post-streptococcal reactive arthritis
  • Lyme arthritis
  • Acute rheumatic fever
  • Reactive arthritis
  • Scurvy
  • Chronic nonbacterial osteomyelitis (CNO) or chronic recurrent multifocal osteomyelitis
  • Non-accidental injury
  • Systemic lupus erythematosus (SLE)
  • Mixed connective tissue disease (MCTD)
  • Sjogren syndrome
  • Scleroderma
  • Sarcoidosis
  • Blau syndrome
  • Arthritis associated with inflammatory bowel diseases
  • Farber disease
  • Benign hypermobility joint syndrome and amplified musculoskeletal pain syndrome )
  • Systemic arthritis
    • Infections (mycoplasma, cat scratch disease, bacterial endocarditis, Lyme disease)
    • acute rheumatic fever, syndrome of periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis (PFAPA syndrome)
    • autoinflammatory syndromes, systemic vasculitis (polyarteritis nodosa, Kawasaki disease)
    • Inflammatory bowel disease, malignancy (leukaemia, lymphoma, neuroblastoma),
    • Castleman disease, Enthesitis related arthritis. Apophysitis (especially Osgood-Schlatter, Sever disease),
    • Inflammatory bowel diseases (IBD), chronic recurrent multifocal osteomyelitis (CRMO)
    • Amplified musculoskeletal pain syndrome.

Complications

• Leg-length discrepancy
• Joint contracture

Management

• Immediately refer all patients with suspected or confirmed juvenile idiopathic arthritis to a paediatric rheumatologist and prescribe an NSAID to relieve symptoms
• Avoid live (attenuated) vaccines in patients taking immunosuppressive drugs; killed (or inactivated) vaccines are safe (although the immune response maybe suboptimal) and yearly influenza vaccination is recommended
• Difficult management and some need immunosuppression
• Steroids for myocarditis or tamponade
• Anti-tumour necrosis factor drugs may have a role
• Methotrexate and other steroid sparing agents have been used

References

• Juvenile Idiopathic Arthritis (JIA)
• Diagnosis and management of juvenile idiopathic arthritis