Persistent severe polyuria after renal transplant.

Area of Science:

• Endocrinology
• Genetics
• Nephrology

Background:

• Polydipsia and polyuria are hallmark symptoms of diabetes insipidus (DI).
• DI can stem from insufficient vasopressin (cranial DI) or impaired kidney response (nephrogenic DI).
• Distinguishing between DI subtypes poses clinical challenges.

Purpose of the Study:

• To investigate a patient with a long-standing misdiagnosis of autosomal dominant nephrogenic DI.
• To identify the underlying genetic cause of DI in a patient with end-stage renal failure and post-transplant polyuria.
• To highlight the complexities in diagnosing DI subtypes.

Main Methods:

• Case report of a 44-year-old male with a family history of DI.
• Review of clinical history including diagnosis of autosomal dominant nephrogenic DI in infancy and progression to end-stage renal failure.
• Analysis of persistent polyuria after renal transplantation.
• Genetic investigation to identify a novel mutation.

Main Results:

• The patient, initially diagnosed with autosomal dominant nephrogenic DI, was found to have been misdiagnosed.
• Further investigations revealed a novel mutation responsible for autosomal dominant cranial DI.
• The patient experienced end-stage renal failure at age 40 and persistent polyuria post-renal transplant.

Conclusions:

• Misdiagnosis of DI subtypes can occur, even with a strong family history.
• Genetic analysis is crucial for accurate DI diagnosis and identifying novel mutations.
• This case underscores the importance of re-evaluating diagnoses when clinical presentation is atypical or persistent.