Bone disorders after organ transplantation

Predictors of avascular necrosis of bone in long-term survivors of hematopoietic cell transplantation

BACKGROUND

Avascular necrosis (AVN) is a debilitating condition reported after chronic steroid use. The purpose of this study was to describe the magnitude of risk in individuals who survived >or=1 years after hematopoietic cell transplantation (HCT), and to investigate the role of immunosuppressive agents such as prednisone, tacrolimus (FK506), mycophenolate mofetil (MMF), and cyclosporine (CSA) in the development of AVN after HCT.

METHODS

Using a retrospective study design, the authors followed 1346 eligible patients for the development of AVN. Cumulative incidence was calculated taking into consideration competing risk from death and disease recurrence. Cox proportional regression techniques were used to identify associated risk factors.

RESULTS

The median age at HCT was 34 years (range, 7 months-69 years), and median length of follow-up for those surviving was 8.2 years. Seventy-five patients developed AVN of 160 joints. The cumulative incidence of AVN at 10 years was 2.9% after autologous HCT, 5.4% after allogeneic matched related donor HCT, and 15% after unrelated donor HCT (P<.001 compared with autologous HCT recipients). For allogeneic transplant recipients, male sex (relative risk [RR], 2.1; 95% confidence interval [95% CI], 1.1-4.0); presence of chronic graft-versus-host disease (RR, 2.2); and exposure to CSA, FK506, prednisone, and MMF rendered patients at increased risk, especially in patients with a history of exposure to >or=3 drugs (RR, 9.2; 95% CI, 2.42-35.24).

CONCLUSIONS

Future studies examining the pathogenetic mechanism underlying AVN should help develop targeted interventions to prevent this chronic debilitating condition.

Bone mineral densities in individuals with Gilbert's syndrome: a cross-sectional, case-control pilot study

BACKGROUND

Unconjugated bilirubin inhibits osteoblastic proliferative activity in vitro, raising the possibility that Gilbert's syndrome (GS) patients are at increased risk of osteoporosis.

OBJECTIVES

To compare bone mineral density (BMD), serum parathyroid hormone (PTH), C-telopeptide (CTX) and osteocalcin levels in GS subjects versus matched controls in a cross-sectional, case-control study.

METHODS

BMD determinations were obtained with central dual energy x-ray absorptiometry. Serum PTH, CTX and osteocalcin levels were measured by enzyme immunoassay.

RESULTS

A total of 17 GS and 30 control subjects were studied. Overall, there were no significant differences in BMD, PTH, CTX or osteocalcin levels between the two groups. However, when older (older than 40 years of age) and younger (40 years of age and younger) cohorts were considered separately, the older GS cohort had significantly decreased total hip BMD, T scores and Z scores, and femoral neck BMD, T scores and Z scores (P<0.005 for each parameter, respectively) compared with older control subjects. Serum osteocalcin levels were lower in the older versus younger GS cohort (P=0.006). An inverse correlation existed between all subjects' serum unconjugated bilirubin levels and total body BMD determinations (r=-0.42; P=0.04). On univariate analysis, the association between serum unconjugated bilirubin and total body BMD was not significant (P=0.066), nor was serum unconjugated bilirubin identified as a risk factor for low BMD when entered into multivariate analyses.

CONCLUSIONS

The results of the present pilot study warrant further research involving larger numbers of subjects and longitudinal measurements to determine whether GS is associated with decreased BMD, particularly in older GS subjects.