# A puzzling renal Fanconi syndrome

## TL;DR

This paper reports a rare genetic cause of Fanconi syndrome with varied symptoms and early kidney issues in some patients.

## Contribution

The study expands the known phenotypic spectrum of Fanconi renotubular syndrome type 3 (FRTS3) caused by the EHHADH gene variant.

## Key findings

- FRTS3 caused by the p.E3K variant in EHHADH shows variable symptoms, including early kidney dysfunction.
- Some family members exhibited only mild symptoms like glucosuria, while others had full Fanconi syndrome and rickets.
- This case highlights broader variability in FRTS3 than previously reported in the literature.

## Abstract

Renal Fanconi syndrome (FS) can be either acquired or inherited. When FS presents at a young age, it is typically inherited, with cystinosis being the most common cause. In this report we describe a rare cause of autosomal dominant Fanconi syndrome, Fanconi renotubular syndrome type 3 (FRTS3), caused by the already reported heterozygous p.E3K variant in the EHHADH gene. Only two FRTS3 families have been reported in the literature, and the kidney function was stated as normal or only slightly decreased into late life. Our family expands the spectrum of FRTS3, with some individuals showing only glucosuria and mild low-molecular-weight proteinuria, while others exhibited complete Fanconi syndrome with rickets. Importantly, we observed impairment of kidney function at a young age in our proband, highlighting a broader phenotypic variability associated with FRTS3.