TY - JOUR T1 - Unraveling the Phenotypic Variability of Juvenile Idiopathic Arthritis across Races or Geographic Areas — Key to Understanding Etiology and Genetic Factors? JF - The Journal of Rheumatology JO - J Rheumatol SP - 683 LP - 685 DO - 10.3899/jrheum.160173 VL - 43 IS - 4 AU - ALESSANDRO CONSOLARO AU - ANGELO RAVELLI Y1 - 2016/04/01 UR - http://www.jrheum.org/content/43/4/683.abstract N2 - Juvenile idiopathic arthritis (JIA) comprises a heterogeneous group of illnesses, all displaying joint inflammation, but with distinct clinical phenotypes, disease courses, outcomes, and presumably, genetic background and pathophysiology1. It is the most common rheumatologic condition in children and a major cause of short- and longterm disability. The current International League of Associations for Rheumatology (ILAR) classification recognizes 7 disease categories, defined on the basis of the clinical and laboratory features present in the first 6 months of illness2.Although the etiology and pathogenesis of JIA are still poorly understood, it is hypothesized that a genetically susceptible individual could develop an uncontrolled and harmful immune response toward a self-antigen upon exposure to an environmental trigger3. However, although several inciting factors have been suspected, including infectious agents, vaccinations, traumatisms, and maternal smoking, proof is still elusive.Instead, there is strong evidence for a genetic predisposition to JIA4. The importance of genetic determinants has been demonstrated by instances of familial aggregation of JIA and by the monozygotic twin concordance rate of 25%–40%. In addition, numerous associations between human leukocyte antigen (HLA) polymorphisms and JIA subtypes have been reported. Recent genome-wide studies in individuals of European ancestry have identified a number of new susceptibility loci also in non-HLA regions4.Over the past 3 decades, several epidemiologic surveys have documented a remarkable, yet unexplained, disparity in the prevalence of JIA subtypes among different geographic areas or racial/ethnic groups5,6,7,8,9,10,11,12,13. In Western countries, the most common category is oligoarthritis, but this form is rare in India, New Zealand, The Middle East, and South Africa, where polyarthritis predominates. Systemic arthritis accounts for an increased proportion of childhood arthritis in Asia, … Address correspondence to Prof. A. Ravelli, Pediatria II, Istituto G. Gaslini, via G. Gaslini 5, 16147 Genoa, Italy. E-mail: angeloravelli{at}gaslini.org ER -