Diabetes insipidus, nephrogenic type 2

Diabetes Insipidus, Nephrogenic Type 2

Diabetes insipidus, nephrogenic type 2 (NDI type 2) is a rare genetic disorder characterized by the kidney's inability to respond to the antidiuretic hormone vasopressin. This condition results in the excretion of large volumes of dilute urine, leading to dehydration and an imbalance of electrolytes in the body.

Pathophysiology

NDI type 2 is caused by mutations in the AQP2 gene, which encodes the aquaporin-2 water channel. Aquaporin-2 is responsible for reabsorbing water in the collecting ducts of the kidney. In individuals with NDI type 2, the aquaporin-2 channels are either not produced correctly or are non-functional, leading to impaired water reabsorption and excessive urination.

Genetics

The condition is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutated gene, one from each parent, to be affected. Carriers of a single mutated gene typically do not show symptoms.

Symptoms

The primary symptom of NDI type 2 is polyuria, which is the production of abnormally large volumes of urine. This can lead to:

• Polydipsia (excessive thirst)
• Dehydration
• Electrolyte imbalances, such as hypernatremia

Diagnosis

Diagnosis of NDI type 2 involves:

• Clinical evaluation of symptoms
• Water deprivation test to assess the kidney's ability to concentrate urine
• Genetic testing to identify mutations in the AQP2 gene

Treatment

Management of NDI type 2 focuses on:

• Ensuring adequate hydration
• Dietary modifications to manage electrolyte balance
• Use of medications such as thiazide diuretics and non-steroidal anti-inflammatory drugs (NSAIDs) to reduce urine output

Prognosis

With proper management, individuals with NDI type 2 can lead normal lives, although they must remain vigilant about maintaining hydration and monitoring their electrolyte levels.

Also see

• Diabetes insipidus
• Vasopressin
• Aquaporin
• Electrolyte imbalance