Hypophosphatemic osteomalacia and renal Fanconi syndrome induced by low-dose adefovir dipivoxil: a case report and literature review suggesting ethnic predisposition

Fanconi syndrome induced by adefovir dipivoxil: a case report and clinical review

More than 150 cases of Fanconi syndrome (FS) or hypophosphatemia osteomalacia induced by low-dose adefovir dipivoxil (ADV) have been reported since 2002, when ADV was introduced for the long-term treatment of hepatitis B virus (HBV) infection. Because the life expectancy of HBV-infected individuals has increased, the adverse effects of long-term treatment with antiviral therapies are increasingly observed, and nephrotoxicity is one of the most severe adverse effects of ADV. Therefore, the number of cases may be far higher than reported. Moreover, ADV-induced FS is often misdiagnosed or diagnosed long after it first develops. ADV-induced FS may seriously decrease patient quality of life and lead to bone fractures and even disability. Although progress has been made in the identification of biomarkers and treatments, few systematic clinical guidelines or clinical reviews for FS induced by ADV have been reported. In this study, we highlighted the recent progress toward understanding of FS induced by ADV, described a clinical case, and summarized the primary characteristics and laboratory findings of this disease.

Follow-Up of Adefovir Dipivoxil Induced Osteomalacia: Clinical Characteristics and Genetic Predictors

Adefovir dipivoxil (ADV) is widely used for chronic hepatitis B therapy in China. To explore the clinical features and prognosis of ADV-induced osteomalacia and to analyze the association between osteomalacia and genetic variants in 51 drug transporters genes. Clinical and follow-up data of the ADV-treated patients were collected. Target capture sequencing was used to identify genetic variations of 51 drug transporter genes. A total of 193 hepatitis B patients treated with ADV were enrolled, of whom 140 had osteomalacia. The other 53 without osteomalacia were included in the control group. The median duration of ADV treatment before the onset of osteomalacia was 6.5 years (range:1.5–7 years). We found that most patients with osteomalacia had hypophosphatemia, high serum alkaline phosphatase levels, hypouricemia, nondiabetic glycosuria, proteinuria. Stopping ADV administration, supplementing calcitriol and calcium were effective treatments. During 3–6 months of follow-up, the clinical symptoms and biochemical indicators of patients with osteomalacia have been significantly improved. There was no significant difference in duration of adefovir treatment in patients with or without osteomalacia (p = 0.791). Through regression analysis, we found that age was a risk factor for osteomalacia [per 1 year, odds ratio (OR), 1.053; 95% confidence interval (95% CI), 1.020–1.087; p = 0.015]. 1992 single nucleotide variants were found using target capture sequencing. However, the associations of genetic variants of 51 drug transporter genes and the risk of osteomalacia were negligible. Osteomalacia is prone to occur in patients with chronic hepatitis B treated with long-term ADV at a therapeutic dose. After standard treatment, the prognosis is mostly good. We failed to find genetic variants that can predict the risk of ADV-induced osteomalacia.

Tenofovir Alafenamide Rescues Renal Tubules in Patients with Chronic Hepatitis B

Nucles(t)ide analogs (NAs) are effective for chronic hepatitis B (CHB). NAs suppress hepatic decompensation and hepatocarcinogenesis, leading to a dramatic improvement of the natural course of patients with CHB. However, renal dysfunction is becoming an important issue for the management of CHB. Renal dysfunction develops in patients with the long-term treatment of NAs including adefovir dipivoxil and tenofovir disoproxil fumarate. Recently, several studies have reported that the newly approved tenofovir alafenamide (TAF) has a safe profile for the kidney due to greater plasma stability. In this mini-review, we discuss the effectiveness of switching to TAF for NAs-related renal tubular dysfunction in patients with CHB.

Cross-sectional retrospective analysis of clinical characteristics of chronic hepatitis B patients with oral antiviral treatment in eastern China

BACKGROUND

In China, more than 20 million patients with chronic hepatitis B need antiviral treatment. Side effects of antiviral treatment such as renal complications can be problematic, particularly in an aging population.

METHODS

The data were retrospectively extracted from the hospital medical charts of five centers in eastern China from January 1 to December 31, 2018.

RESULTS

A total of 8309 patients with CHB was enrolled in this study. The median age of the patients was 46 years. The prevalence of diabetes mellitus, hypertension, and hepatic cirrhosis was respectively 3.49%, 4.42%, and 23.72%. The prevalence of these comorbidities increased with age (P < 0.001). Of the patients with CHB, 5332 had complete renal function results. Among them, patients with an estimated glomerular filtration rate of < 60 mL/min/1.73m² accounted for 4.14%, and those with proteinuria for 8.33%. According to the definition of chronic kidney disease, the proportion of patients with chronic kidney disease was 11.37%. The prevalence of chronic kidney disease increased with age (P < 0.001). In a multivariate analysis, age group [odds ratio (OR) = 2.387], diabetes mellitus (OR = 1.486), hypertension (OR = 2.557), hepatic cirrhosis (OR = 1.295), and a history of exposure to adefovir dipivoxil (OR = 1.644) were significantly associated with CKD (P < 0.05). Among patients with CKD, 17.66% (107/606) had a history of lamivudine exposure, and 34.65% (210/606) had a history of nucleotide analogue exposure CONCLUSION: The management of Chinese patients with CHB should take into consideration age, previous medication history, and renal impairment.

Osteomalacia and renal failure due to Fanconi syndrome caused by long-term low-dose Adefovir Dipivoxil: a case report

Background

Progressive bone pain and fracture and abnormal positron emission tomography combined with a computed tomography are main reasons for the oncologists suspecting bone tumor. During the patient’s medical treatment, the oncologists’ unfamiliarity with adverse reactions to anti-HBV drugs were main reason for the long-term exposure to the drug and the adverse reaction (ADR) experienced by the patient.

Case presentation

A 63-year-old Chinese man had a 27-month history of progressive generalized bone pain combined with spontaneous fractures. Positron emission tomography combined with a computed tomography, revealed an abnormal increase in ribose metabolism and low positron serum inorganic phosphorus concentration (0.7; 0.78–1.65 mmol/L). Serum creatinine level was 252 μmol/L (53–97) μmol/L, and glomerular filtration rate was 22.79 mL/min/1.73 m². The patient was referred to a multidisciplinary clinic to clarify the diagnosis of myeloma or bone tumor for further treatment in 2017. His medical history revealed that he had a 30-year history of chronic hepatitis B infection. He had received lamivudine at a daily dose of 100 mg for 19 years (1990 to 2009), which had been changed to adefovir (10 mg/day) owing to lamivudine resistance in 2009. Based on the changes in the patient’s laboratory markers and the results of emission computed tomography and other radiographic findings, adefovir-induced hypophosphatemic osteomalacia due to acquired renal Fanconi syndrome was suspected by the clinical pharmacist. Considerable clinical improvement was observed after adefovir discontinuation and the administration of entecavir (1.0 mg, every other day).

Conclusion

Fanconi syndrome with osteomalacia can develop in patients with chronic hepatitis B infection being treated with adefovir at a conventional low dosage of 10 mg/day. This case highlights the importance of ADR as a differential diagnosis and the need of pharmacists with drug safety expertise expert in the patient management.

Retrospective analysis of the clinical characteristics of adefovir dipivoxil-induced Fanconi's syndrome in the Chinese population

WHAT IS KNOWN AND OBJECTIVE

To explore the clinical characteristics of adefovir dipivoxil-induced Fanconi's syndrome in the Chinese population and provide a reference for rational drug use in the clinic.

METHODS

By searching the CNKI, Wanfang, Chinese VIP, PubMed/MEDLINE, Web of Knowledge, Ovid, Elsevier and SpringerLink databases during 1 January 2008 to 31 December 2019, 78 studies of ADV-induced Fanconi's syndrome involving a total of 110 patients were collected and analysed retrospectively.

RESULTS AND DISCUSSION

Prolonged usage of adefovir dipivoxil at low doses to treat hepatitis B might cause Fanconi's syndrome as the first symptom, especially for use over 12 months.The main clinical manifestation was bone pain accompanied by hypophosphataemia, elevated alkaline phosphatase (ALP), urine glycosuria and urine protein. X-rays and bone mineral density (BMD) examinations were mainly used to characterized osteoporosis. The patients had pain relief within 1 week to 1 month, and the biochemical indicators returned to normal within from 2 to 4 months.

WHAT IS NEW AND CONCLUSION

Sufficient attention is required before and during exposure to long-term ADV therapy. The clinical picture, laboratory and radiograph alterations are important clues for ADV-induced Fanconi's syndrome.

Low-dose adefovir dipivoxil-induced hypophosphatemia osteomalacia in five chronic hepatitis B virus-infected patients. Is low-dose adefovir dipivoxil-induced nephrotoxicity completely reversible?

Adefovir dipivoxil (ADV) is one of the most important nucleostide analogues currently in use for the treatment of chronic hepatitis B virus (HBV) infection. Low-dose ADV-induced nephrotoxicity in most cases was reported to be reversible after the discontinuation of ADV or by decreasing the dose of ADV. In our study, we have 5 documented cases of low-dose ADV-induced hypophosphatemia osteomalacia with or without Fanconi syndrome which were diagnosed in our hospital between 2010 and 2017. Three patients were observed to have a full recovery after the discontinuation of ADV. Two patients had persistently elevated urine β₂-microglobulin levels and out of these two patients, one patient had persistent hypophosphatemia after the cessation of ADV. These cases illustrated that the use of low-dose ADV increased the risk of nephrotoxicity, and in some patients, low-dose ADV-induced nephrotoxicity was not completely reversible. Patients of East Asian origin, especially those with a low body mass index, were prone to a relatively higher risk of developing low-dose ADV-induced nephrotoxicity; therefore, it was worth paying attention to the side effects caused by low-dose ADV.

Hypophosphatemic Osteomalacia Associated with Adefovir-induced Fanconi Syndrome Initially Diagnosed as Diabetic Kidney Disease and Vitamin D Deficiency

A 68-year-old man with type 2 diabetes mellitus and chronic hepatitis B infection was referred to the nephrology department before planned surgery for hepatocellular carcinoma. He had been receiving low-dose adefovir dipivoxil (ADV) for 11 years. Laboratory findings revealed impaired re-absorption in the proximal renal tubules. He had been diagnosed with diabetic kidney disease and osteomalacia due to vitamin D deficiency; thus, ADV was not discontinued until he was referred to us. In this case, concomitant diabetes mellitus and vitamin D deficiency might have prevented the early diagnosis of ADV-induced Fanconi syndrome.

Adefovir dipivoxil induced hypophosphatemic osteomalacia in chronic hepatitis B: a comparative study of Chinese and foreign case series

BACKGROUND

Adefovir dipivoxil (ADV)-induced renal tubular dysfunction and hypophosphatemic osteomalacia (HO) have been given great consideration in the past few years. However, no standard guidance is available due to a lack of powerful evidence from appropriate long-term prospective case-control studies and variations in the definition of renal adverse events. The aim of this study is to clarify clinical features of ADV-related HO in Chinese chronic hepatitis B patients with long-term ADV treatment in Chinese and non-Chinese comparative case series.

METHODS

Retrieval of case reports was based on Pubmed, CNKI, Wan Fang and VIP databases using the key words adefovir dipivoxil, hypophosphatemia, osteomalacia and Fanconi syndrome. We divided patients into Chinese (C group) and Foreign (F group) groups according to their nationality. Comparisons involving demographics, clinical manifestations, tests, treatment and prognosis were conducted between the two groups.

RESULTS

Of the patients screened, 120 Chinese patients were identified in the C group, and 32 non-Chinese patients were identified in the F group. The average age of the C group was younger than that of the F group (51.89 years ±10.96 years versus 56.47 years ±11.36 years, t = - 2.084, P = 0.039). No significant difference was found in gender (male to female, 3.29:1 versus 3:1, χ ²  = 0.039, P = 0.844). Although there was no significant difference in the duration of ADV therapy before ostalgia onset, the C group tended to develop adverse events earlier, by 2-3 years, while the F group developed adverse events at 4-5 years (Z = - 1.517, P = 0.129). Prognosis was good after adjustment of the ADV dose and supplemental administration of phosphate and calcitriol. Time to resolution of tubular dysfunction was commenced at the first month, and Chinese patients were more prone to recover in the first 3 months than non-Chinese patients (91.3% of patients in the C group versus 56.3% in the F group, Z = - 3.013, P = 0.003).

CONCLUSIONS

Sufficient attention is required for middle-aged males before and during exposure to long-term ADV therapy, regardless of nationality. The clinical picture, laboratory and radiograph alterations are important clues for those patients and are usually characterized by polyarthralgia, renal tubular dysfunction and mineralization defects. Implementation of an early renal tubular injury index is recommended for patients with higher risk, which would prevent further renal injury.

Clinical features of hypophosphatemic osteomalacia induced by long-term low-dose adefovir dipivoxil

Objective

To investigate the predictors of hypophosphatemic osteomalacia induced by adefovir dipivoxil (ADV) and to monitor for early detection.

Patients and methods

Hospitalized patients who were diagnosed with ADV-related hypo-phosphatemic osteomalacia were recruited and retrospectively analyzed in our hospital from January 2012 to December 2016. A telephone interview was conducted at 1, 3, 6, 9, 12, and 24 months after cessation of ADV.

Results

In the 8 patients enrolled in the study, the hypophosphatemic osteomalacia symptoms developed at an average of 5.14 (4–7) years since ADV treatment (10 mg/d). The average alkaline phosphatase (ALP) level was 279.50 (137–548) U/L, which was significantly higher than the normal level (45–125 U/L). The serum phosphorus level was an average of 0.59 (0.43–0.69) mmol/L, which was lower than the normal range (2.06–2.60 mmol/L). Serum calcium levels of the enrolled patients remained within normal limits. Reduced estimated glomerular filtration rate (eGFR <29 mL/min/1.73 m²) was seen in 4 cases. The clinical manifestations were mainly progressive systemic bone and joint pain, frequent fractures, trouble in walking, height reduction (4–6 cm), and so on. After cessation of ADV, symptoms like bone pain resolved gradually. Serum phosphorus level restored to normal in 4.5 months after the withdrawal of ADV. However, in 4 patients, renal function failed to return to normal in 24 months.

Conclusion

More attention should be paid to the duration of ADV treatment. The level of serum phosphorus and ALP, as well as renal function, should be monitored for early detection of potential adverse drug reactions.

Hypophosphatemia predicts a failure to recover from adefovir-related renal injury after dose reduction in lamivudine-resistant hepatitis B patients

AIM

In chronic hepatitis B patients receiving 10 mg adefovir, dose reduction is recommended when renal injury appears. However, recovery is not always achieved and markers that recommend switching to another antiviral agent are unknown. We investigated adefovir-related renal injury, recovery after dose reduction, and their predictors.

METHODS

The renal injury in 77 chronic hepatitis B patients receiving 10 mg adefovir and recovery after dose reduction to alternate day administration in those with adefovir-related renal injury were assessed. The predictors for >20% estimated glomerular filtration rate (eGFR) decline following treatment with 10 mg adefovir and for >20% eGFR recovery after dose reduction were investigated.

RESULTS

The adefovir dose was reduced in 26 patients (34%) at 59 ± 30 (mean ± standard deviation) months of 10 mg adefovir treatment because of decreases in eGFR (cumulative incidence 27%), serum phosphorus (9%), and uric acid (16%) levels, and increases in alkaline phosphatase (20%), bone type alkaline phosphatase (18%), urinary α1-microglobulin (18%), and urinary N-acetyl-β-D-glucosaminidase (18%) levels. The only significant predictor for >20% eGFR decline was age ≥50 years at the start of 10 mg adefovir treatment. The cumulative eGFR recovery rate was 42% at 42 ± 27 months after dose reduction, and ≥2.5 mg/dL serum phosphorus level at dose reduction was the only significant predictor for >20% eGFR recovery after dose reduction.

CONCLUSION

Patients aged ≥50 years are predisposed to adefovir-related renal injury and switching to another antiviral agent rather than adefovir dose reduction is recommended when hypophosphatemia is observed.

Osteomalacia induced by long-term low-dose adefovir dipivoxil: Clinical characteristics and genetic predictors

CONTEXT

Adefovir dipivoxil (ADV) was an important cause of adult-onset hypophosphatemic osteomalacia. However, its clinical characteristics and mechanisms have not been well defined.

OBJECTIVE

The objective of the study was to summarize the clinical characteristics of ADV-induced osteomalacia and to explore the association between ADV-associated tubulopathy and polymorphisms in genes encoding drug transporters.

DESIGN, SETTING, PATIENTS, AND MAIN OUTCOME MEASURE

Seventy-six affected patients were clinically studied. The SLC22A6 and ABCC2 genes were screened and compared with healthy people from the HapMap.

RESULTS

Hypophosphatemia, high serum alkaline phosphatase (ALP) levels, hypouricemia, nondiabetic glycosuria, proteinuria, metabolic acidosis and high bone turnover markers were the main metabolic characteristics. Fractures and pseudofractures occurred in 39 patients. Stopping ADV administration, supplementing calcitriol and calcium was effective during the follow-up period. Single SNP analysis revealed a higher percentage of the G/A genotype at c.2934 in exon 22 of the ABCC2 gene (rs3740070) in patients than in healthy people (12% [7 of 58 patients] vs. 0% [0 of 45 patients]; P=0.017), while there was no subject with homozygosity for the A allele at c.2934.

CONCLUSIONS

ADV can be nephrotoxic at a conventional dosage. The G/A genotype at c.2934 of the ABCC2 gene may be a predictor of patients at greater risk for developing ADV-associated tubulopathy. Larger case-control studies are needed to further verify this finding.

Nucleos(t)ide analogues for the prevention of hepatitis B recurrence after liver transplantation do not affect serum phosphorus levels

BACKGROUND

Nucleos(t)ide analogues (NAs) constitute the backbone of treatment for the prevention of hepatitis B virus recurrence after liver transplantation (LT). Decline in serum phosphorus levels is a common side effect of nucleotide therapy. Our aim was to assess the impact of nucleotide treatment on the occurrence of hypophosphatemia after LT and determine possible predictors.

METHODS

We retrospectively analyzed data from liver transplant recipients who had been transplanted for various indications. All patients were evaluated every 3 months. Each patient was considered to be having hypophosphatemia when at least one value of serum phosphorus ≤2.5 mg/dL was detected.

RESULTS

In total, 109 patients [83 males (76%)] with a mean age of 55±10 years were included. 46/67 (67%) patients with hepatitis B received a nucleotide. The rate of hypophosphatemia (55%) was not different between patients with hepatitis B and those transplanted for other indications (62%). Patients receiving a nucleotide did not run a greater risk of hypophosphatemia than patients receiving only nucleosides (59% vs. 48%, P=0.39). Male gender and everolimus use were associated with the occurrence of hypophosphatemia in patients with hepatitis B. In multivariate analysis only gender was associated with hypophosphatemia (odds ratio 11.43, 95%CI -2.11 to -0.49; P=0.0025).

CONCLUSIONS

Hypophosphatemia occurs in more than half of liver transplant recipients regardless of the indication for LT. Male gender and everolimus use seem to predispose to hypophosphatemia, whereas the type of antiviral agent does not.

Urinary β-2 Microglobulin Levels Sensitively Altered in an Osteomalacia Patient Receiving Add-on Adefovir Dipivoxil Therapy for Hepatitis B Virus Infection

Adefovir dipivoxil (ADV) is effective for hepatitis B virus (HBV) infection; however, ADV may provoke renal injury resulting in osteomalacia, and this side effect is seldom recognized until bone fractures emerge. We herein present a 66-year-old woman with HBV infection who received ADV for 6 years. Although she exhibited no sign of bone fractures, her urinary β-2 microglobulin (β2MG) level increased to 83,837 μg/L and scintigraphy revealed minimal fractures of the third rib. ADV was subsequently reduced and her urinary β2MG rapidly fell to 3,637 μg/L. Conversely, her urinary N-acetyl-β-D-glucosaminidase, and serum phosphate, alkaline phosphatase levels did not respond.

Osteomalacia and Fanconi's syndrome caused by long-term low-dose adefovir dipivoxil

WHAT IS KNOWN AND OBJECTIVE

Adefovir dipivoxil (ADV) is recommended for patients infected with lamivudine-refractory hepatitis B virus (HBV). We report a case of low-dose ADV-induced hypophosphatemic osteomalacia that initially presented as diffuse musculoskeletal pain.

CASE SUMMARY

A 59-year-old Chinese man reported an 18-month history of severe chest wall pain and multiple bone pain during the previous 4 months with no antecedent trauma. There was no clinical evidence of an infectious, inflammatory or malignant process. Medical history showed that the patient had a history of chronic hepatitis B infection, and receiving lamivudine at a daily dose of 100 mg for 70 months. Lamivudine was changed to adefovir (10 mg/day) for the past 42 months. His serum inorganic phosphorus concentration was significantly low (0·4 mmol/l; 0·81-1·5 mmol/L), and the result of a urine routine test was abnormal. Combined with unbearable bone pain, spontaneous fractures, changes in laboratory markers and the result of ECT and other radiographic findings, the diagnosis of Fanconi's syndrome with osteomalacia was established. Dramatic clinical, laboratory and imaging improvement was observed after ADV discontinuation.

WHATS IS NEW AND CONCLUSION

This case indicates that Fanconi's syndrome with osteomalacia can be acquired by a chronic hepatitis B patient taking ADV at a conventional dosage of 10 mg/day. Therefore, patients with HBV treated with long-term ADV should be regularly monitored for renal function, serum calcium and serum phosphate. Urine testing for ion concentration should also be undertaken.

Predictors of kidney tubular dysfunction induced by adefovir treatment for chronic hepatitis B

AIM: To investigate the predictors of proximal kidney tubular dysfunction (PKTD) induced by adefovir dipivoxil (ADV) treatment for chronic hepatitis B.

METHODS: Seventy-nine patients (age at the evaluation of PKTD: 56.9 ± 10.7 years) with chronic hepatitis B undergoing long-term oral antiviral nucleos(t)ide analogue treatment were consecutively recruited. PKTD was defined by the presence of at least two of the following five abnormalities: phosphate diabetes, nondiabetic glucosuria, metabolic acidosis, β₂-microglobulinuria, or renal hypouricemia. The single-nucleotide polymorphisms (SNPs) in the SLC22A6 gene encoding human organic anion transporter 1 (hOAT1) and ABCC2 encoding multidrug resistance protein 2 (MRP2) were analyzed using the TaqMan Allelic Discrimination Demonstration Kit.

RESULTS: Nine (30.0%) of the 30 ADV-treated patients were diagnosed with PKTD, while no patients without ADV developed PKTD (P < 0.001). Three patients with ADV were diagnosed with symptomatic osteomalacia. Among the patients who took ADV, those with PKTD were of higher age at initiation, had significantly longer treatment duration, and had a significantly lower body mass index than those without PKTD. The incidence of PKTD dramatically increased after 96 mo from the start of ADV administration. In contrast, the SNPs were not correlated with PKTD. Logistic regression analysis extracted older age at initiation (OR = 5.0, 95%CI: 1.1-23.4; P = 0.040) and longer treatment duration (OR = 3.2, 95%CI: 1.2-8.6; P = 0.020) as significant factors associated with PKTD.

CONCLUSION: Our results suggest that the tubular function of the kidney of older patients undergoing long-term ADV treatment should be carefully evaluated.

Adefovir-induced Fanconi syndrome: diagnostic pearls and perils of late or missed diagnosis

Low-dose adefovir therapy has been increasingly recognised as a cause of Fanconi syndrome. Being relatively novel, early diagnosis is both fraught with difficulty and yet of paramount importance given its far-reaching consequences, many of which are amenable to treatment. We discuss a patient who presented with hypokalemia and other electrolyte abnormalities suggestive of Fanconi syndrome whilst on adefovir for hepatitis B. A trans-tubular potassium gradient (TTKG = 9.4) and urinary fractional phosphate excretion (39.4 %) consistent with renal potassium and phosphate wasting together with euglycemic glycosuria, aminoaciduria and hypophosphatemic osteomalacia supported the diagnosis of adefovir-induced Fanconi syndrome. With the cessation of the culprit drug, the patient has achieved partial recovery after 9 months. A high index of suspicion coupled with regular symptom surveillance and electrolyte monitoring is recommended in the course of adefovir therapy.

Corrective osteotomy in femoral non-union in drug-induced hypophosphataemic osteomalacia

Adefovir/tenofovir are commonly used antiviral agents in the treatment of chronic hepatitis B infection (CHB). We report a case of CHB-related cirrhosis presenting with sequential femoral neck fractures. Operative reduction and fixation was performed. Laboratory result and imaging was consistent with hypophosphataemic osteomalacia. He had bilateral femoral neck non-union and presented with a new left side subtrochanteric femoral fracture. Corrective osteotomy and cephalomedullary fixation was performed. The fractures healed in 6 months after correction of the hypophosphataemia.

Two Cases of Hypophosphatemic Osteomalacia After Long-term Low Dose Adefovir Therapy in Chronic Hepatitis B and Literature Review

Adefovir dipivoxil (ADV) is a nucleotide used as long-term therapy of chronic hepatitis B. Many published reports have shown that long-term high-dose therapy with adefovir can be associated with proximal renal tubular dysfunction resulting in significant hypophosphatemia, renal insufficiency and osteomalacia. We have encountered two patients who developed evidence of hypophosphatemic osteomalacia while on long-term low-dose adefovir therapy for chronic hepatitis B. We report on its clinical features and its potential resolution with cessation of the drug and supplementation with phosphate. We also reviewed the other published cases associated with hypophosphatemic osteomalacia after low-dose adefovir therapy. The symptoms and the hypophosphatemia improved after cessation of the drug and supplementation with phosphate in most cases. Patients taking adefovir long-term should receive regular investigation of the phosphate level and renal function.