Background Juvenile idiopathic arthritis (JIA) – chronic articular disease related to immune system dysfunctions. JIA course and complications have genetic background.
Objectives We evaluated features of JIA and related bone mineralization and metabolism changes with VDR polymorphic genotypes in children with JIA.
Methods 71 children with active JIA were included in our study. For assessment of JIA activity we used onset age, duration of morning stiffness, number of active joints, white blood cells (WBC) count, Westergren erythrocyte sedimentation rate (ESR), C-reactive protein. Physician global assessment (PGA) of disease activity, measured on a 10-cm visual analog scale (VAS) where 0 = no activity and 10 = maximum activity; parent/patient global assessment of well-being, measured on a 10-cm VAS where 0 = very well and 10 = very poor. We utilized combined indexes for assessment disease activity – JADAS10, JADAS27, JADAS71, CDAI, DAS and DAS28 were utilized. Bone mineralization was measured in all children by dual-energy X-ray absorptiometry (DXA) of lumbar spine (LS) at L1-L4 (Hologic QDR 4500C densitometer with reference pediatric database). Densitometry parameters, such as bone area (BA, cm2), bone mineral content (BMC, grams) and bone mineral density (BMD, measured in grams/cm2 and in Z score, SD) were all evaluated. Low bone mineral density (LBMD) for chronological age was defined by Z score < 2 SD, according to the recommendation of the International Society for Clinical Densitometry, 2007.
For assessment of bone metabolism the following measures were used: osteocalcin (bone gla-protein, a marker of osteosynthesis), carboxyterminal telopeptide of type I collagen (CTX -products of collagen I type degradation and a marker of bone resorption) and parathyroid hormone (PTH) by routine imunoenzyme methods. Also levels of total calcium (Ca), ionized calcium (Ca++), inorganic phosphate (Pi) and total alkaline phosphatase (ALP) were determined.
Molecular testing – ApaI and BsmI polymorphisms of VDR gene polymorphisms were detected by restriction fragment length polymorphism.
Results There were no significant differences of ApaI and BsmI polymorphic genotypes, alleles and haplotypes distribution between children with normal and low BMD. BsmI polymorphism was associated with arthritis activity only in boys and ApaI polymorphism was related to JIA activity only in girls.
Girls with AA genotypes ApaI VDR had higher BMD and BMD-Zscore compare with aa and Aa carriers respectively. Boys with B allele (BB+Bb genotypes) BsmI VDR had lower RAI, DAS and JADAS 10. The same changes were observed in JADAS 27 (p=0,04) and JADAS 71 (p=0,04).
Conclusions differences in JIA activity and bone mineralization related to VDR genetic polymorphisms confirms the multi-potential role of vitamin D which regulates on immune system and bone metabolism.
Disclosure of Interest None Declared
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