| Abstract|| |
Previous studies have suggested that loss of bone mineral density (BMD) frequently occurs in patients with chronic viral liver disease, presenting with histologically proven liver cirrhosis. However, little is known about the occurrence of bone disease in non-cirrhotic patients with chronic hepatitis C virus (HCV) infection. Furthermore, to the best of our knowledge, such an effect has never been studied in pediatric renal transplant recipients. The aim of this study was to assess the impact of HCV infection on BMD in pediatric renal transplant patients. We performed a cross-sectional study to assess BMD and HCV in 83 patients who received living renal allotransplants in the Mansoura Urology and Nephrology Center between 1983 and 2005. The mean age of the study patients at transplantation was 13.4 ± 2.9 years; there were 53 males (63.9%) and 30 females (36.1%). BMD was studied using dual energy X-ray absorptiometry at various time intervals up to 16 years after transplantation (mean duration after transplantation was 48 ± 34 months, range 12- 192 months). Thirty-three patients tested positive for HCV-RNA (positive group) and 50 patients were negative (negative group), and we compared the BMD between the two groups. Before transplantation, 58 patients (69.9%) were on maintenance hemodialysis, four (4.8%) were on peritoneal dialysis and 21 (25.3%) were pre-emptive. Among the HCV-positive group, six patients (18.2%) had osteoporosis, 17 (51.5%) had osteopenia and ten (30.3%) had normal BMD. In the HCV-negative group, ten patients (20.0%) had osteoporosis, 24 (48.0%) had osteopenia and 16 (32.0%) had normal BMD. The difference was not significant between the two groups (P = 0.9). Also, there was no significant difference in the serum creatinine, calcium, phosphorus and parathormone levels between the two groups. Our results suggest that chronic HCV infection does not pose a risk for low BMD in pediatric renal transplant recipients.
|How to cite this article:|
El-Husseini A, Sabry A, Hassan R, Sobh M. Effect of chronic hepatitis C virus infection on bone mineral density in pediatric renal transplant recipients. Saudi J Kidney Dis Transpl 2013;24:917-24
|How to cite this URL:|
El-Husseini A, Sabry A, Hassan R, Sobh M. Effect of chronic hepatitis C virus infection on bone mineral density in pediatric renal transplant recipients. Saudi J Kidney Dis Transpl [serial online] 2013 [cited 2019 Nov 15];24:917-24. Available from: http://www.sjkdt.org/text.asp?2013/24/5/917/118078
| Introduction|| |
The association between osteopenia and various types of liver disease has been described for more than half a century.  The clinical course of osteopenia has been best characterized in the chronic cholestatic liver diseases, but is also known to occur in alcoholic, autoimmune and viral liver disease. ,
The epidemiology of hepatitis C virus (HCV) infection in the developing world has not been well characterized. The prevalence rates of HCV infection across the world fluctuate and are difficult to calculate because of the latent nature of the disease prior to clinical presentation. The prevalence of HCV among the Egyptian population is one of the highest registered in all age groups. , The national prevalence rate of HCV-antibody positivity has been estimated to be between 10% and 13%.  Egypt's mass campaigns of parenteral anti-schistosomal therapy may represent the world's largest iatrogenic transmission of blood-borne pathogens.  Barsoum has reported in his survey an average HCV prevalence of 32.8% among patients with end-stage renal disease in Egypt and in nine other developing countries.  We previously reported that 65% of the Egyptian adult and 39% of the Egyptian pediatric renal transplant populations are HCV positive. , Also, we have reported that 65% of our pediatric kidney transplant recipients had osteopenia or osteoporosis. 
Low bone mass and deterioration of bone tissue, leading to increased bone fragility and risk of fracture, are the defining characteristics of osteoporosis. In its early asymptomatic stage, osteoporosis can only be detected by measuring the bone mineral density (BMD). Early detection of reduced BMD is an important means of prevention, and dual energy X-ray absorptiometry (DEXA) is the most helpful modality. The risk of fracture increases 1.5- to 3-fold or more for each standard deviation (SD) decrease in BMD from that of a young adult. The World Health Organization (WHO) defined osteopenia as a Z-score between -1 and -2.5 and osteoporosis as a Z-score less than or equal to 2.5. 
The prevalence of osteoporosis among patients with chronic liver disease ranges from 10% to 60%. , The highest prevalence is observed in cholestatic liver disease and alcoholic liver disease. Gallego-Rojo et al reported that the prevalence of osteoporosis in patients with cirrhosis secondary to hepatitis B or C was nearly 50%.  In such patients, osteomalacia may also lead to a decrease in BMD; however, hepatic osteomalacia demonstrated by histomorphometric methods is very rare.  The most common reason for the decrease in BMD in these conditions is the decreased absorption of vitamin D from the small intestine. , The relationship between osteopenic bone disease and non-cholestatic liver disease is less well defined. Yousfi et al suggested a possible relationship between viral hepatitis B and C and end-stage hepatitis C with low BMD. 
Limited data are available on the contribution of chronic HCV infection to the development of bone disease in the renal transplant population. We studied whether HCV infection causes a decrease in the BMD in our pediatric renal transplant patients. In contrast to the other studies, in this study, we report on BMD and bone disease in patients with non-cirrhotic chronic HCV-related liver disease among the pediatric renal transplant recipients.
| Patients and Methods|| |
In this cross-sectional study, 83 pediatric renal transplant patients who received living donor kidney transplants at the Mansoura Urology and Nephrology Center, Mansoura, Egypt, at various time intervals were included. The selection criteria were patients with functioning graft at least 12 months post-renal transplantation.
Our renal transplant program policy is that all donors should be HCV negative without any evidence of liver disease, all recipients should have normal liver function before transplantation and any patient with elevated liver enzymes should be thoroughly evaluated. All patients with chronic HCV infection were followed-up until normalization of liver enzymes for at least six months prior to receiving their renal allograft.
The following baseline data were obtained on each subject: Age, sex, cause of renal failure, duration of renal disease prior to transplantation, duration and type of dialysis, duration after renal transplantation, immunosuppressive regimen and acute and chronic rejection.
All subjects underwent biochemical evaluation of their renal allograft function and calcium metabolism. Measurement of BMD was performed by DEXA using a lunar DFXMD 7517 machine (Lunar Corp., Madison, WI, USA). All children were evaluated by the same apparatus. Quality assurance was performed daily. The BMD results were expressed as gm/cm 3 and measurement was made on the lumbar spine at L2-4. The Z score is the number of SD an individual BMD value deviates from the mean value in race- and sex-matched young adults and children. As recommended by the WHO, we defined osteopenia as a Z-score between -1 and -2.5 and osteoporosis as a Z-score less than or equal to 2.5.  BMD was studied using DEXA at various time intervals up to 16 years after transplantation (mean duration after transplantation was 48 ± 34 months, range 12-192 months).
The serum creatinine, calcium, phosphorus, albumin and alkaline phosphatase levels were measured using a synchron CX7 system (Beckman Auto Analyzer Instruments Inc., Indianapolis, IN, USA). The creatinine clearance was calculated using the Schwartz formula for children up to 18 years  and using the Cockroft-Gault formula in adults aged more than 18 years.  Intact parathyroid hormone (PTH) was measured by a two-site radioimmunoassay for intact PTH (Diagnostic Product Corp., Los Angeles, CA, USA). Serum samples were stored at -30°C until testing. Antibodies against HCV (anti-HCV) were tested with commercial enzyme immunoassays (Abbott Diagnostics, Wiesbaden, Germany). HBV-DNA and HCV-RNA were measured by a quantitative polymerase chain reaction (PCR) (Abbott Diagnostics). The virological status (positive or negative) was determined using HCV-RNA PCR.
| Statistical Analysis|| |
Variables are given as mean ± SD unless stated otherwise. Chi-square test was used to compare the prevalence of the non-parametric variables while differences between variables were analyzed using the paired Student's t-test. A P-value of <0.05 was considered statistically significant. All analyses was performed using the Statistical Package for Social Science (SPSS, Chicago, IL, USA) version 11.0 for windows. 
| Results|| |
Of the 83 patients studied, 53 (64%) were males and 30 (36%) were females. Fifty-eight patients (69.9%) were on maintenance hemodialysis prior to transplantation while four (4.8%) were on peritoneal dialysis and 21 (25.3%) were pre-emptive. Their mean age at transplantation was 13.4 ± 2.9 years; the mean donor age was 38.4 ± 8.6 years. The demographic- and disease-related data at the time of enrollment are listed in [Table 1].
Thirty patients tested positive (36%) for HCV while the remaining 50 patients (64%) were negative.
Bone mineral density
Sixteen patients had osteoporosis (19%), 41 had osteopenia (49%) and 26 (32%) had normal BMD according to the WHO classification. Among the HCV-positive patients, six (18.2%) had osteoporosis, 17 (51.5%) had osteopenia and ten patients (30.3%) had normal BMD. In the HCV-negative patients, 10 (20%) had osteoporosis, 24 (48.0%) had osteopenia and 16 (32%) had normal BMD (P = 0.64). The prevalence of osteopenia and osteoporosis in the HCV-positive and -negative groups is shown in [Table 2] and [Figure 1].
|Table 2: Bone mineral density measurement in the 83 pediatric renal transplant patients.|
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|Figure 1: Bone mineral density in the hepatitis C virus-positive versus the hepatitis C virus-negative groups.|
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Comparison between HCV-positive and -negative groups
No significant difference was observed between the HCV-positive and HCV-negative groups regarding the BMD score (-2.28 ± 1.5 versus -2.30 ± 1.39, respectively; P = 0.9), recipients' and donors' age, hemoglobin levels, serum calcium, phosphorus, PTH and albumin levels, mean number of graft biopsies and acute rejection and serum creatinine at one and three months [Table 3]. Also, there was no significant difference between patients with normal and abnormal BMD and their age, number of acute rejections and total steroid dose in the first three months, serum calcium, phosphorus and PTH and HCV status [Table 4]. None of the patients reported a past history of bone fracture at the time of enrollment.
|Table 3: Laboratory parameters in the hepatitis C virus-positive and -negative groups.|
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|Table 4: Comparison between transplant patients with normal and low bone mineral density.|
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Post-transplantation immunosuppressive medications
Patients transplanted before 1989 (n = 9) were treated with a maintenance immunosuppressive regimen comprising of daily prednisolone between 0.1 and 0.15 mg/kg and azathioprine 2 mg/kg. A triple regimen with prednisolone, cyclosporine A and azathioprine has been introduced in 1989 (n = 52). Cyclosporine A was administered in a dose to maintain whole-blood trough levels between 100 and 150 ng/mL. Tacrolimus and mycophenolate mofetil were introduced in 1997 and prednisone was tapered down to cessation (n = 22). The cumulative steroid dose was 12 ± 4 g, with a daily maintenance dose of 0.1 mg/kg, and there was no difference in the mean cumulative steroid dose in both groups (P = 0.342).
The overall graft survival in the study patients at 1, 5 and 10 years was 93.4%, 73.3% and 48.2%, respectively, while the patient survival at 1, 5 and 10 years was 97.6%, 87.8% and 75.3%, respectively.
| Discussion|| |
Limited data are available on the contribution of chronic HCV infection to the development of bone disease in renal transplant patients. To the best of our knowledge, such an effect has never been studied thus far in pediatric renal transplant recipients. Our study of 83 patients reveals a high prevalence of osteopenia and osteoporosis in pediatric renal transplant patients as 68% of the study patients had abnormal BMD. However, no significant difference was observed between HCV-positive and -negative patients concerning the number of osteopenic/ osteoporotic patients as well as the BMD scores. The effect of chronic HCV infection on bone disease is poorly understood. Although some studies have reported an increased prevalence of osteoporosis in patients with chronic HCV, , others did not find this effect, ,, especially in non-cirrhotic HCV-positive patients. Lorio et al recently published a meta-analysis on BMD in patients with hemophilia. They found six studies reporting on HCV-positive patients. There was a trend toward a direct correlation between reduction of BMD in hemophilic patients and the percentage of HCV-infected patients, but it was not statistically significant (P = 0.193 for the regression coefficient). 
The spectrum of bone disease attributed to HCV infection suggests a complex relationship between chronic HCV infection and bone metabolism. , In general, patients with more advanced clinical and histologic stages of liver fibrosis have more severe skeletal disease.  Previous studies investigating the link between HCV and bone disease had small patient numbers in addition to cohorts of mixed gender with varying degrees of liver damage, which hindered the interpretation of the findings. 
The etiologic mechanism of osteopenia in HCV is unknown. Although loss of BMD frequently occurs in patients with chronic viral liver disease presenting with histologically proven liver cirrhosis, little is known about the prevalence of osteoporosis in non-cirrhotic patients with chronic hepatitis C; the biological mechanisms underlying this relationship are complex and poorly understood. An alteration of the vitamin D-parathyroid hormone axis may be involved and could be partially responsible for shifting the balance in bone metabolism toward bone resorption and decrease of bone mass. Decreased concentration in 25-hydroxy vitamin D levels has been reported in hepatitis C patients, and they were decreasing with increasing severity of the liver disease. Furthermore, chronic inflammation of the liver is accompanied by a systemic increase in cytokines, which can stimulate bone resorption. Moreover, in patients with viral chronic hepatitis and osteodystrophy, increased levels of bone resorption markers were found, which inversely correlated with BMD. 
Schiefke et al reported for the first time on the effect of non-cirrhotic viral hepatitis on BMD. They studied 30 HCV-RNA-positive patients; 20% had osteoporosis and 60% had osteopenia. Non-cirrhotic chronic hepatitis C patients showed a decreased BMD.  Our results are discordant from what has been reported by them. However, there are major differences between our study and their study; firstly, our patients were younger while the mean age of their study patients was 49 years (range 26-77 years); secondly, 72% of their patients were females, who are known to have some degree of osteoporosis; and, lastly, 7% were smokers and there was no control group.
In agreement with our results, Yenice et al in 2006  did not find any significant difference between patients who were HCV positive and matched healthy controls with respect to BMD. They studied the BMD in 45 HCV-positive patients and compared it with 60 healthy controls. The authors concluded that there was no significant association between chronic viral hepatitis and decreased BMD. However, the patients included in this study had moderate and severe hepatitis proven by liver biopsy, which was not performed in our study, and BMD was measured in the medial phalanx of the 2 nd , 3 rd and 4 th fingers of the non-dominant hand. Additionally, all the patients were on ribavirin and interferon therapy, which could affect BMD.
Contrary to all these studies in which bone metabolism was evaluated in cirrhotic patients, our study exclusively included pediatric transplant recipients with chronic liver disease with no clinical or histological findings of cirrhosis. However, it should be mentioned that our patients were of the pediatric age group and showed no clinical signs of chronic liver disease. If the same condition was studied in adults with a longer and profound effect of HCV on the liver structure and function, the results could have been different.
Kidney transplant recipients are exposed to multiple factors that lead to osteoporosis after kidney transplantation. Short- and long-term longitudinal studies revealed a strong decline of BMD after transplantation.  Pathogenesis of post-transplant bone loss involves both pre-existing risk factors (such as hyperparathyroidism) and the adverse effects of immunosuppressive therapy. Glucocorticoid-induced suppression of bone formation is the most important factor in the genesis of early and long-term bone loss.  Not a single published clinical trial in renal transplant patients, even in adults, has studied the effect of HCV infection on BMD.
The major limitations of our study were absence of a sex- and age-matched control group and also the cross-sectional nature of our study. Studying pediatric transplant recipients with no prior history of cirrhosis or chronic active hepatitis may underestimate the effect of liver disease on BMD. On the other hand, it was beneficial to check the impact of HCV infection itself (rather than the effect of liver impairment) on the BMD. Also, one other limitation of this study was that we did not measure the serum vitamin D or the urinary calcium excretion levels.
In summary, we examined the effect of chronic HCV infection on BMD in pediatric renal transplant recipients. We found that chronic HCV infection does not increase the risk of development of metabolic bone disease in this cohort. Large-scale prospective studies with long-term follow-up should be performed for a better assessment of the effects of HCV on bone mass and of the underlying mechanism linking the two diseases.
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Division of Nephrology, University of Kentucky, 800 Rose Street, MN 560, Lexington, KY 40536
[Table 1], [Table 2], [Table 3], [Table 4]