Clinical features, genetic background, and outcome in infants with urinary tract infection and type IV renal tubular acidosis.

Background: Type IV renal tubular acidosis (RTA) is a severe complication of urinary tract infection (UTI) in infants. A detailed clinical and molecular analysis is still lacking.

Methods: Infants with UTI who exhibited features of type IV RTA were prospectively enrolled. Clinical, laboratory, and image characteristics and sequencing of genes responsible for phenotype were determined with follow-up.

Results: The study cohort included 12 infants (9 males, age 1-8 months). All exhibited typical type IV RTA such as hyperkalemia with low transtubular potassium gradient, hyperchloremic metabolic acidosis with positive urine anion gap, hypovolemic hyponatremia with renal salt wasting, and high plasma renin and aldosterone levels. Seven had hyperkalemia-related arrhythmia and two of them developed life-threatening ventricular tachycardia. With prompt therapy, all clinical and biochemical abnormalities resolved within 1 week. Five had normal urinary tract anatomy, and three of them carried genetic variants on NR3C2. Three variants, c.1645T>G (S549A), c.538G>A (V180I), and c.1-2C>G, on NR3C2 were identified in four patients. During follow-up, none of them had recurrent type IV RTA, but four developed renal scaring.

Conclusions: Genetic mutation on NR3C2 may contribute to the development of type IV RTA as a complication of UTI in infants without identifiable risk factors, such as urinary tract anomalies.