# When Two Syndromes Collide: Managing Fanconi and Refeeding Syndrome in a Single Patient

## TL;DR

A patient with AIDS and substance abuse developed severe electrolyte issues from a rare side effect of a medication and worsened by refeeding.

## Contribution

This case highlights a rare instance of Fanconi syndrome caused by tenofovir alafenamide and worsened by refeeding syndrome.

## Key findings

- The patient developed severe hypophosphatemia and electrolyte imbalances linked to tenofovir alafenamide (TAF).
- Refeeding syndrome exacerbated the electrolyte abnormalities and contributed to the patient's death.
- TAF-related Fanconi syndrome is rare and often overlooked compared to disoproxil fumarate-related cases.

## Abstract

Refeeding syndrome is the potentially fatal shift in fluids and electrolytes that may occur in malnourished patients after receiving artificial refeeding. Its hallmark feature is hypophosphatemia, although other electrolytes might also be affected. Fanconi syndrome is a generalized dysfunction of the proximal tubule characterized by proximal renal tubular acidosis (RTA), phosphaturia, glycosuria, aminoaciduria, and proteinuria. The etiology of Fanconi syndrome can be either acquired or inherited, and drugs, among them tenofovir, are a common acquired cause of this disease. We present the case of a patient with AIDS and polysubstance abuse who was admitted due to pneumonia, completed treatment, was then started on antiretroviral medication (ART) that included tenofovir alafenamide (TAF) and began presenting severe episodes of hypophosphatemia along with other electrolyte imbalances, leading the workup denoted in the case, severe complications and finally to the patient's demise. Most cases of tenofovir-related Fanconi syndrome are related to tenofovir disoproxil fumarate, but very few cases have been reported with TAF. Our case highlights this rare complication of therapy with TAF and how artificial feeding can contribute to severe electrolyte abnormalities and worsen outcomes.