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Abstract: SA-PO359

A Novel Aquaporin 2 Insertion Mutation in a Chinese Family with Autosomal Dominant Nephrogenic Diabetes Insipidus and Chronic Renal Failure

Session Information

Category: Trainee Case Report

  • 1002 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Tsai, Ping-Huang, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
  • Cheng, Chih-Jen, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
  • Lin, Shih-Hua P., Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
Introduction

Mutations in aquaporin 2 (AQP2) cause mostly autosomal recessive or rarely autosomal dominant nephrogenic diabetes insipidus (NDI). Patients with autosomal dominant NDI usually exhibit less phenotype and have mutations in the carboxyl-terminal tail important intracellular routing of the AQP2. We described a family of autosomal dominant NDI carried a novel AQP2 mutation but presented a severe phenotype, which led to early-onset renal failure.

Case Description

A 26-year-old Chinese female manifested polyuria, polydipsia, and nocturia after birth. Her family history was non-revealing. She did not have non-obstructive hydronephrosis and never received NSAID or thiazide to treat her polyuria. Pertinent laboratory investigations showed abnormal renal function with serum creatinine 3.4 mg/dL, and hyperchloremic metabolic acidosis (chloride 115, HCO3- 19 mmol/L), persistently low urine osmolality (around 50-100 mOsm/kg.H2O) and markedly increased serum von Willebrand factor and coagulation factor VIII in response to desamino-8-D-arginine AVP (DDAVP) test. Direct sequencing of AVPR2 and AQP2 gene showed two nucleotide GC insertion at c.755 of AQP2, resulting in a frameshift mutation (p.R253Dfs*82, +52 AA) and altering the amino acid sequence between R254 to A271. Of note, her one-year-old son also exhibited severe polyuria two days after birth and was found carrying the same mutation.

Discussion

We presented the first autosomal dominant NDI family with a severe phenotype, including early-onset polyuria in the neonatal period and renal failure in early adulthood. The functional experiment focusing on autosomal dominant AQP2 mutations in the C-terminal end is warranted.