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Table 1 Similarities and differences between RA and JRA/JIA

From: Is juvenile rheumatoid arthritis/juvenile idiopathic arthritis different from rheumatoid arthritis?

Feature RA JRA/JIA
Classification criteria Single disease with different manifestations Phenotypically and genetically distinct subtypes
Gender Females > males Females > males except in systemic arthritis
Age of onset Puberty plus; peak 4th to 5th decade Polyarticular: throughout childhood; peak 1-3 years of age
   Pauciarticular: early childhood; peak 1-2 years of age
   Systemic: throughout childhood; no peak
Extended multiplex families Present Very rare
Family history of other autoimmune disorders Present Present
Typical ocular involvement Keratoconjunctivitis sicca Chronic anterior uveitis
Prevalence 10/1000 0.86/1000
Ethnic distribution Reported in all populations EOPA is rare in non-Caucasians
HLA association HLA DRB1*0401, 0404, 0101 in Caucasians EOPA: HLA-A2, -DR5, -DR8, -DPB1*0201. (HLA-DR4 is protective)
   Late pauciarticular: HLA-B27
   Polyarticular: HLA-DR1, -DR4
Shared epitope Defined; amino acid positions 67-74 of third hypervariable region Not described
Growth/developmental issues Rare Common
Pathophysiology Th1-mediated disease Th1-mediated disease (Pauciarticular: Also Th2-mediated)
Autoantibodies IgM RF common IgM RF rare
Natural history Majority have long-term disability Fewer than half have long-term disability
  1. EOPA, early-onset pauciarticular arthritis; HLA, human leukocyte antigen; JIA, juvenile idiopathic arthritis; JRA, juvenile rheumatoid arthritis; RA, rheumatoid arthritis; RF, rheumatoid factor; Th, T helper.