BONE-DISEASE IN CHILDREN AND ADOLESCENTS UNDERGOING SUCCESSFUL RENAL-TRANSPLANTATION

Little is known about the renal and severity of bone disease in childr en undergoing successful renal transplantation. To address this issue, 37 patients with stable renal function 3.2 +/- 1.7 years after transp lantation (Tx) underwent iliac crest bone biopsy. The mean age of pati ents was 12 +/- 2.0 years 36 had received cadaveric renal grafts, wher eas 11 had undergone living-related Tx. Immunosuppressive drugs includ ed cyclosporine 0.17 +/- 0.4 mg/day, prednisone 7.5 +/- 2.1 mg/kg/ day , and either azathioprine 1.6 +/- 0.9 mg/kg/day or mycophenolate mofet il 30 +/- 3 mg/kg/day. In addition to quantitative bone histomorphomet ry, the bone mineral content (BMC) of the lumbar spine was measured by dual energy X-ray absorptiometry (DXA) in 24/47 patients. Thirty-one transplant recipients had normal bone formation (N-Bfr). 11 had mild h yperparathyroidism (HPT) and 5 had adynamic skeletal lesions (AD). The interval since Tx, duration of dialysis before Tx and cumulative pred nisone dose did not differ among groups. Trabecular bone area was high est in subjects with HPT. Unexpectedly, eroded bone perimeter exceeded normal reference values both in patients with AD and in those with N- Bfr; the osteoid area and osteoid perimeter were also elevated in thes e two groups. Hyperparathyroidism improved or resolved after Tx in all 14 subjects with this skeletal lesion prior to Tx. but one patient de veloped AD after Tx. Bone histology did not change after Tx in those w ith N-Bfr during regular dialysis, but bone formation increased after Tx in two of three patients with AD during regular dialysis. Z-scores for height in pre-pubertal patients after Tx were below age-appropriat e values in each histologic subgroup, but values did not differ among groups. Z-scores for bone mineral content at the lumbar spine were als o less than age-predicted values, -0.67 +/- 1.2. After adjusting for t he degree of growth retardation, height-adjusted z-scores for lumbar s pine BMC after Tx were above normal in all three histologic groups (0. 68 +/- 1.0). The results suggest that reductions in bone mass and post -transplant osteoporosis are nor prominent findings in pediatric renal transplant recipients when the influence of growth retardation on bon e mass measurements by DXA is carefully considered.