While only two infants so far have been identified with NSIAD, the condition may not be rare, according to Stephen Rosenthal, MD, professor of pediatric endocrinology and co-lead author of the study with endocrinology fellow Brian Feldman, MD, PhD. "Water retention is a common problem, and with new tools we can examine our long-held assumptions about its cause," Rosenthal said. "There may be mutations in other components of the V2 receptor signaling cascade that result in inappropriate antidiuresis."
In fact, after Feldman presented this work at an international meeting last September, he said, "Several physicians indicated they were now considering the diagnosis of NSIAD as an explanation for low sodium levels in their pediatric patients."
The discovery of NSIAD began in 2003 after two unrelated baby boys, each about three months old, were referred to UCSF Children's Hospital with symptoms of fluid overload and strikingly low levels of sodium in their blood. The first child suffered from severe irritability. A few months later, the second infant was admitted with generalized seizures.
Doctors in the pediatric endocrinology and pediatric nephrology services at UCSF Children's Hospital determined that each baby's kidneys were inappropriately retaining water, and the excess fluids were diluting blood sodium levels.
The usual diagnosis for this condition is Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) -- a common medical problem whose cause was discovered almost 50 years ago to be an overabundance of vasopressin (also called antidiuretic hormone). However, when the UCSF doctors took advantage of new, rapid tests to measure vasopressin in these two infants, they found no detectable levels of the hormone in either child's bloodstream. They concluded
Source:University of California - San Francisco