Purpose The purpose of this study was to investigate nutritional Vitamin D (Vit D) deficiency and changes in bone mineral density (BMD) over 1 year post-transplant in a predominantly African American (AA) pediatric kidney transplant (Tx) population.

Methods In this prospective controlled study, pediatric renal transplant recipients (age 2-21) had 25-hydroxy VitD levels measured and BMD assessed by Dual X-ray absorptiometry (DXA) scan at baseline. Baseline VitD and Height-adjusted BMD z scores of AA Tx were compared with non-AA Tx and healthy AA pediatric controls. Tx with low BMD (z<-1) had DXA repeated after 1 year.

Results 84 Tx patients (46 AA,38 others) had baseline VitD measured. Mean Vit D of AA Tx was lower (21.8 ng/ml ±1.4 SEM) than non-AA Tx (29.6±2.1 SEM), p=0.003. Baseline Vit D of AA Tx (n=46) was compared with 71 healthy AA controls. Prevalence of suboptimal VitD status (VitD <30 ng/ml) did not differ between AA Tx (78.2%) compared with AA controls (85.9%). However, the proportion of AA children with severe VitD deficiency (<15 ng/ml) was greater among AA Tx (37%) versus AA controls (16.9 %), p=0.009. All Tx with baseline VitD deficiency were treated with cholecalciferol to achieve Vit D sufficiency (>30 ng/ml). 65 Tx (34 AA,31 others) had baseline DXA which was compared to DXA in 69 AA controls. A greater proportion of both non-AA Tx (20%, p=0.005) and AA Tx (22%, p=0.0007) children had low WB BMD (z<-1) when compared to AA controls (2.9%). Greater prevalence of low Hip BMD (z<-1) was also found among AA Tx (29%) compared to controls (5%), p=0.0006. In the cohort of 14 Tx patients with low baseline BMD (z<-1) who had a DXA scan repeated 1 year post-transplant, hip and spine BMD z scores significantly improved by 0.33 (C.I.=0.17-0.49, p=0.0006) and 0.39 (C.I.=0.06-0.72, p=0.02) SDS respectively. Whole body (WB) BMD z score did not change among Tx.

Conclusion AA Tx children have lower baseline VitD stores compared with non-AA Tx children at the time of transplant. AA Tx are also more likely to have severe Vit D deficiency compared with healthy AA children, and should be monitored and treated. Low WB BMD is more prevalent among all Tx children at baseline, regardless of race. AA Tx are also more likely to have low Hip BMD. Tx children with low baseline BMD show significant improvement in Hip and Spine BMD, but not WB BMD, one year after transplant. Strategies to optimize BMD in pediatric kidney Tx recipients should be further investigated.

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