Nephrogenic Diabetes Insipidus (NDI) is a condition in which the kidneys are unable to respond to the anti-diuretic hormone, vasopressin, resulting in an inability to retain water. Patients affected with this disorder show the characteristic signs of excessive urination and extreme thirst. In congenital forms, the infant is unable to express his thirst, and hence, begins to show other obvious symptoms, including fever, irritability, constipation, anorexia, and a failure to develop, along with severe dehydration. Such children tend to be slightly smaller in size than their counterparts. Even as adults, the height remains slightly shorter than average in patients, although their weight may be normal.
NDI might be suspected in infants showing the above-mentioned symptoms. However, confirmation of the diagnosis requires additional tests, including measurement of plasma osmolality and sodium concentrations, measurement of urine volume and specific gravity, and water deprivation tests. There is no cure for NDI. However, it can be successfully managed. The most important requirement in the management of the condition is a regular intake of water by the patient. Certain medications may help in reducing the rate of urine formation; most notably non-steroidal anti-inflammatory drugs, and thiazide diuretics. When thiazide diuretics are taken, potassium supplements may also be needed. Dietary modifications could include reducing the amount of sodium and protein intake. Patients will need life long monitoring. However, with proper management, a normal life expectancy can be attained. If left untreated, however, the condition can give rise to complications, including brain damage, mental retardation, and even death.
Inherited NDI can be of two types. About 90% of such cases are inherited in an X-linked manner. Only 10% of cases of NDI are transmitted in an autosomal manner. This autosomal form of NDI is caused due to mutations in the Aquaporin-2 (AQP2) gene, located on the long arm of chromosome 12. Interestingly, different mutations in this same gene have been shown to cause both autosomal dominant and recessive forms of NDI.