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Association of polymorphic variants of PTPN22, TNF and VDR genes in children with lupus nephritis: A study in Colombian family triads.

INTRODUCTION
Systemic lupus erythematosus is an autoimmune disease in which the severity varies according to race, sex and age of onset. This variation is also observed in the genetic markers associated with the disease, including PTPN22, VDR and TNF genes. The genetic stratification in different populations worldwide can influence the variability.


OBJECTIVE
To analyze the heritability of PTPN22, VDR and TNF genetic variants and their association with pediatric lupus nephritis in Colombian families.


MATERIALS AND METHODS
We conducted a family-based study including 46 triads (case, father and mother). The variants rs2476601 of PTPN22; rs361525 and rs1800629 of TNF, and TaqI [rs731236], ApaI [rs7975232], BsmI [rs1544410] and FokI [rs2228570] of VDR were genotyped by qPCR. The effects of overtransmission of the risk allele from parents to children and linkage disequilibrium at the VDR and TNF loci were estimated.


RESULTS
We found that allele A of rs2476601 in PTPN22 was distributed among 8.69 % (n=16) of the parents and 19.5 % (n=18) of the cases; this allele was overtransmitted from parents to children 17 times more often than the G allele (p=0.028). TNF and VDR polymorphisms did not exhibit transmission disequilibrium. VDR TaqI, ApaI and BsmI variants exhibited linkage disequilibrium.


CONCLUSION
These findings showed an association between the PTPN22 rs2476601 polymorphism and pediatric lupus nephritis due to its overtransmission in the group of families studied.