# Retrospective review of bladder biopsy instead of skin biopsy provided clue for the diagnosis of neuronal intranuclear inclusion disease

## TL;DR

A patient was diagnosed with a rare neurological disease using a bladder biopsy instead of a skin biopsy, improving diagnostic methods.

## Contribution

This case highlights the use of bladder biopsy for diagnosing neuronal intranuclear inclusion disease when skin biopsy is negative.

## Key findings

- Intranuclear inclusions were identified in bladder tissue, confirming NIID diagnosis.
- MRI showed lesion enlargement at the corticomedullary junction over time.
- Genetic testing confirmed the diagnosis after bladder biopsy findings.

## Abstract

The purpose of this study is to present a case of a patient with a negative skin biopsy who was diagnosed with neuronal intranuclear inclusion disease (NIID) through a retrospective review of a bladder biopsy specimen obtained 10 years ago. The patient initially presented with encephalitis-like symptoms, including fever, headache, and abnormal mental behavior. However, the DWI hyperintensity in the corticomedullary junction indicated the possibility of NIID. Due to the negative results of the skin biopsy, we initially refrained from hastily diagnosing the patient with NIID. However, 6 months later, the patient was readmitted to the hospital due to similar symptoms, and a follow-up MRI showed significant enlargement of the lesions at the corticomedullary junction. This time we identified intranuclear inclusions in her tissue specimens from bladder surgery. Subsequently, genetic testing was performed, leading to the diagnosis of NIID in the patient. Our case report indicates that detecting intranuclear inclusions from previous surgical specimens, rather than relying solely on skin biopsy, could significantly enhance diagnostic methods for NIID.