A gene polymorphism of the phosphorylated glycoprotein, osteopontin, appears to be associated with the prognosis of oligoarticular-onset juvenile idiopathic arthritis, but more data are needed before it is considered a reliable disease marker.
Recently proposed to be a new proinflammatory cytokine, osteopontin plays a role in bone resorption and angiogenesis and is known to mediate a number of inflammatory mechanisms.
The current study, led by Renato Marciano, M.D., of the G. Gaslini Institute and the University of Genova, Italy, involved 73 patients with persistent oligoarticular-onset juvenile idiopathic arthritis (o-JIA) and 46 with extended o-JIA (Ann. Rheum. Dis. 2005; doi:10.1136/ard.2005.040626).
Patients were genotyped for the biallelic insertion/deletion variant at +245 in the first intron of the osteopontin gene, which the researchers had previously found to be in strict linkage with molecular variants in the osteopontin promoter region.
The TG polymorphism in the first intron was identified as allele 1, and the TGTG allele as allele 2. The presence of allele 2 was significantly higher (47/73 or 64%) in the persistent oligoarticular group, compared with patients with the extended form (20/46 or 43%), suggesting a dominant effect of the TGTG allele in o-JIA patients.