# A Rare Case Report of Fanconi Anemia-Associated Nuclease 1 Mutation Causing Nephrotic Syndrome

## TL;DR

A 25-year-old man with a rare FAN1 gene mutation developed kidney disease, showing how this mutation can affect the kidneys in unexpected ways.

## Contribution

This case report presents a rare FAN1 mutation linked to nephrotic syndrome, expanding its known clinical manifestations.

## Key findings

- The patient had nephrotic-range proteinuria and contracted kidneys due to a FAN1 mutation.
- Genetic analysis identified mutations in exons 4 and 12 of the FAN1 gene.
- Conservative treatment reduced proteinuria, but kidney biopsy was not feasible.

## Abstract

A 25-year-old African male patient presented with a history of frothy urination for one month. He had a significant family history of early onset chronic kidney disease (CKD) in his older brother. On evaluation, he was found to have deranged renal function and nephrotic-range proteinuria of 6152 mg/day. Urine examination revealed proteinuria and glycosuria. Viral serology and autoimmune screening results were negative. Ultrasonography revealed contracted kidneys that were not amenable to biopsy. Genetic analysis revealed a Fanconi anemia-associated nuclease 1 (FAN 1) mutation in exon 4 (c.1399G>A) and exon 12 (c.2786A>C). The patient was managed conservatively with a maximum dose of angiotensin receptor blockers with a reduction in proteinuria on follow-up. This case report highlights the rare manifestation of FAN 1 mutation and its variable effects on the kidney.