الفهرس 
Genetic predisposition:
Enthesitis-related arthritis (ERA)Only 14 pages are availabe for public view
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Abstract
Juvenile idiopathic arthritis (JIA) is comprised of a heterogeneous group of several disease subtypes that are characterized by the onset of arthritis without an apparent cause before the age of 16 years and has symptoms lasting at least 6 weeks(1).Seven clinical JIA subtypes are recognized based on the classification of the International League of Associations for Rheumatology (ILAR),oligoarthritis (o-JIA: persistent or extended), polyarthritis (p-JIA: rheumatoid factor-positive or negative), psoriatic arthritis, systemic JIA (s-JIA),enthesitis-related arthritis (ERA) and undifferentiated arthritis(2)The pathogenesis of JIA is still unknown but the interplay of genetic and environmental factors leads to immune dysregulation. Different immune components and cells are involved in the pathogenesis of the disease and an upregulation of different cytokines and chemokines has been observed in serum and synovium of JIA patients(3 Systemic inflammation in s-JIA is closely associated with the dysregulation of the innate immune system driven by proinflammatory cytokine suggesting that it is an auto inflammatory disorder . In particular, IL- 1, IL-6, TNF-α, and IL-18 play a major role in the pathogenesis of s-JIA and the treatment with IL-1 and IL-6 inhibitors has severe effects in s-JIA
patients(4)Polyarticular JIA defined according ILAR as arthritis that affects five or more joints during the first 6 months of disease. This subgroup is further
divided into rheumatoid factor (RF) positive or RF negative, with the former having two or more RF positive tests at least 3 months apart during the first 6 month period(2).