Severe vitamin D deficiency in a patient treated for hepatitis B with tenofovir

With the increasing use of tenofovir disoproxil in the management of HIV and hepatitis B, serious adverse effects, such as renal dysfunction, will inevitably increase in frequency. We describe a case of a patient presenting with hypophosphataemia suggestive of Fanconi's syndrome, but in fact explicable by simple vitamin D deficiency. This emphasizes that while monitoring for adverse effects is recommended, physicians must consider all alternative causes for biochemical abnormalities prior to discontinuing tenofovir and delaying appropriate management.