Hyponatremia resulting from Arginine Vasopressin Receptor 2 gene mutation

Pediatr Nephrol (2007) 22:463466 DOI 10.1007/s00467-006-0344-7

BRIEF REPORT

Hyponatremia resulting from Arginine Vasopressin Receptor 2 gene mutation

David Francisco Bes & Hernn Mendilaharzu &

Raymond G. Fenwick & Elvira Arrizurieta

Received: 7 August 2006 / Revised: 23 September 2006 / Accepted: 25 September 2006 / Published online: 18 November 2006 # IPNA 2006

Abstract Chronic hyponatremia, unless associated with extracellular fluid volume expansion, is an infrequent electrolyte imbalance in pediatrics. We report an infant with chronic hyponatremia suggestive of a syndrome of inappropriate secretion of antidiuretic hormone (SIADH), in the absence of ADH secretion. A mutation was found in the same codon of the gene that results in a loss-of-function of arginine vasopressin receptor 2 (AVPR2) observed in congenital nephrogenic diabetes insipidus. In this case, a gain-of- function of AVPR 2 was found to be responsible for a SIADH-like state.

Keywords Seizure . Syndrome of inappropriate secretion of antidiuretic hormone . AVPR2 . Water excretion . Nephrogenic syndrome of inappropriate antidiuresis . Hypo-osmolarity syndrome of inappropriate antidiuresis

Introduction

Hyponatremia is defined by some authors as a decrease in serum sodium concentration below 136 mEq/l [1, 2], others define it when it is 130 mEq/l or less [3, 4]. Hypotonic hyponatremia represents an excess of water in relation to sodium stores [1]. These may be decreased, increased or essentially normal. Hyponatremia may be further associated with an extracellular fluid volume that is contracted, increased or also essentially normal [1, 2]. In hyponatremia associated with contracted fluid volume, hemodynamic compromise occurs and is what usually determines the patients clinical manifestations. However in hyponatremia associated with normal or increased extracellular volume, neurological symptoms such as seizures are presenting signs that warrant hospital admission [2, 4]. The purpose of this presentation is to describe the diagnosis and outcome of an infant who presented chronic hyponatremia with normal extracellular fluid volume.

D. F. Bes (*)

Department of Pediatrics, Hospital Nacional de Pediatra Prof. Dr. Juan P. Garrahan, Pichincha 1850,Buenos Aires 1245, Argentinae-mail: [email protected]

H. MendilaharzuEndocrinology Service, Hospital Nacional de Pediatra Prof. Dr. Juan P. Garrahan, Buenos Aires, Argentina

R. G. Fenwick Molecular Endocrinology, Quest Diagnostics, Nichols Institute, San Juan Capistrano, CA, USA

E. ArrizurietaDepartamento de Rin Experimental, Instituto de Investigaciones Mdicas Dr. Alfredo Lanari, Universidad de Buenos Aires, Buenos Aires,...