# Diagnosis of Autosomal Dominant Polycystic Kidney Disease in a 66-Year-Old Patient With a Genotype-Phenotype Mismatch

## TL;DR

A 66-year-old man with a rare gene mutation for a kidney disease was diagnosed despite having a typically milder form of the condition.

## Contribution

Highlights a genotype-phenotype mismatch in ADPKD and the challenges of managing older patients.

## Key findings

- The patient had an IFT140 gene mutation, usually linked to a milder ADPKD phenotype.
- Despite this, the patient was classified as high risk for disease progression using the MIC tool.
- Tolvaptan is not studied in patients over 65, complicating treatment decisions.

## Abstract

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder characterized by the progressive development of renal cysts, ultimately leading to chronic kidney disease (CKD) and end-stage renal disease (ESRD). Patients are typically diagnosed in their 20s or 30s, and the majority have a parent with a known history of the condition. The most common gene mutations associated with ADPKD are PKD1 and PKD2, although other mutations have also been identified. Kidney enlargement rates can vary and serve as a marker for ADPKD progression and the eventual decline in kidney function. The Mayo Imaging Classification (MIC) tool assesses the risk of progression by incorporating height-adjusted total kidney volume (htTKV) and the patient's age. Tolvaptan is recommended for patients at high risk of progression, although it has not been studied in individuals over the age of 65.

This case report focuses on the diagnosis and management of ADPKD in a 66-year-old male with no known family history of the condition. Genetic testing revealed an IFT140 gene mutation, typically associated with a less severe phenotype. However, the patient was classified as 1C according to the MIC, indicating a high risk of disease progression. This case underscores the challenges of managing severe disease in older patients, given the limited research available for this age group.