IMPE2023 Poster Presentations Multisystem Endocrine Disorders (5 abstracts)
1Hospital Italiano, Buenos Aires, Argentina. 2Hospital Prof. Dr. Juan P. Garrahan, Buenos Aires, Argentina
Introduction: Nephrogenic syndrome of inappropriate diuresis (NSIAD) is a rare X-linked genetic disease characterized by a gain-of-function mutation of the V2 receptor. Clinical presentation is similar to inappropriate secretion of ADH (SIADH) including euvolemic hyponatremia, decreased plasma osmolarity, and increased urinary osmolarity, but low or undetectable levels of antidiuretic hormone.
Objective: To report a case of nephrogenic syndrome of inappropriate antidiuresis.
Clinical case: A 24 months old boy with antecedent of 2 episodes of hyponatremia was referred to our institution for a multidisciplinary evaluation. His antecedents were: At 7 months of age he had had the first episode of asymptomatic hyponatremia (Na 119-123 mEq/L) undergoing acute respiratory syncytial virus bronchiolitis. After hospitalization he had been discharged with high oral sodium intake. At 8 months he had developed a second episode of severe hyponatremia in the context of diarrhea with hemodynamic decompensation, and altered sensorium. He had required hospitalization in an intensive care unit and had been discharged again with high oral sodium intake. Complementary studies showed: Normal thyroid, adrenocortical and renal function with normal plasma renin and aldosterone levels; normal brain magnetic resonance imaging. Genetic study of 50 mutations for Cystic Fibrosis was negative. When he was admitted at our hospital, sodium intake was restricted for 48 hours, and he developed hyponatremia (118 milliequivalents/L) associated with high urinary sodium (101 milliequivalents/L); decreased plasma osmolarity 243 mOsm/kg (Normal range 285-305) with high urinary osmolarity (460mOsm/kg); hypouricemia (1.4 mg/dl) with high fractional excretion of uric acid (11%). Antidiuretic hormone level was < 1 pg/ml. With the presumptive diagnosis of NSIAD, AVPR2 sequencing revealed a previously described hemizygous activating mutation (p.Arg137Cys). The mother presented this variant in a heterozygous state. During this period, the patient's maternal grandfather presented an episode of severe symptomatic hyponatremia in a context of elective prostate surgery.
Conclusion: NSIAD is a rare disease that should be suspected in patients with chronic euvolemic hyponatremia. This entity is X-linked dominant. Women are usually asymptomatic carriers. It is extremely important to carry out a confirmatory molecular study due to its prognostic and therapeutic implications.