Chest Deformity and Disability due to Tenofovir-Induced Hypophosphatemic Osteomalacia: Case Report and Call for Improved Global Access to Laboratory Testing

Millions of people worldwide take tenofovir disoproxil fumarate (TDF) for the treatment of human immunodeficiency virus (HIV) and/or hepatitis B infection. Although generally safe and well tolerated, clinicians need to be aware that TDF can cause proximal renal tubular dysfunction and loss of bone mineral density, especially in patients with concomitant renal disease or other risk factors. We present the case of a patient with chronic HIV infection and urethral stricture who developed TDF-related proximal renal tubular dysfunction with hypophosphatemia and osteomalacia, presenting with bone pains, skeletal deformity, and disability. We review risk factors for TDF-related renal tubular toxicity and recommendations for monitoring creatinine, phosphate, alkaline phosphatase, and urinalysis.

Reversal of Proximal Renal Tubular Dysfunction after Nucleotide Analogue Withdrawal in Chronic Hepatitis B

Aims. Proximal renal tubular dysfunction (PRTD) is an infrequent complication after nucleotide analogue therapy. We evaluated the outcomes of PRTD and nephrotoxicity after nucleotide analogue withdrawal in chronic hepatitis B (CHB). Methods. A longitudinal follow-up study was performed in patients with PRTD after nucleotide analogue discontinuation. Serum and urine were collected at baseline and every 3 months for one year. The fractional excretion of phosphate (PO4), uric acid (UA), and potassium and tubular maximal reabsorption rate of PO4 to glomerular filtration rate (TmPO4/GFR) were calculated. Renal losses were defined based on the criteria of substance losses. Subclinical PRTD and overt PRTD were diagnosed when 2 and ≥3 criteria were identified. Results. Eight subclinical and eight overt PRTD patients were enrolled. After nucleotide analogue withdrawal, there were overall improvements in GFR, serum PO4, and UA. Renal loss of PO4, UA, protein, and β2-microglobulin reduced over time. At one year, complete reversal of PRTD was seen in 13 patients (81.2%). Improvements in PRTD were seen in all but one patient. Conclusion. One year after nucleotide analogue withdrawal, PRTD was resolved in most patients. Changes in TmPO4/GFR, urinary protein, and β2-microglobulin indicate that urinary biomarkers may represent an early sign of PRTD recovery.

Hypophosphatemic Rickets: Presenting Features of Fanconi—Bickel Syndrome

Fanconi-Bickel Syndrome (FBS) is a rare variety of glycogen storage disease (GSD). Characterized by massive hepatomegaly due to glycogen accumulation, severe hypophosphatemic rickets, and marked growth retardation due to proximal renal tubular dysfunction. We report a young boy presented as hypophosphatemic rickets with hepatomegaly and subsequently diagnosed as FBS.