Diabetes insipidus, nephrogenic type 3

Diabetes Insipidus, Nephrogenic Type 3

Diabetes insipidus, nephrogenic type 3 is a rare genetic disorder characterized by the kidney's inability to respond to antidiuretic hormone (ADH), also known as vasopressin. This condition leads to excessive urination and thirst, as the kidneys fail to concentrate urine effectively.

Pathophysiology

Nephrogenic diabetes insipidus (NDI) occurs when the kidneys are unable to respond to ADH, which normally acts on the collecting ducts of the nephron to promote water reabsorption. In nephrogenic type 3, this resistance is due to mutations in the AQP2 gene, which encodes the aquaporin-2 water channel. These mutations impair the function or expression of aquaporin-2, preventing water reabsorption and resulting in the excretion of large volumes of dilute urine.

Genetics

Nephrogenic diabetes insipidus, nephrogenic type 3, is inherited in an autosomal recessive manner. This means that an individual must inherit two copies of the mutated gene, one from each parent, to manifest the disease. Carriers, who have only one copy of the mutation, typically do not show symptoms.

Clinical Presentation

Patients with nephrogenic diabetes insipidus, nephrogenic type 3, present with polyuria (excessive urination) and polydipsia (excessive thirst). These symptoms often appear in infancy or early childhood. If left untreated, the condition can lead to dehydration, electrolyte imbalances, and growth retardation.

Diagnosis

Diagnosis of nephrogenic diabetes insipidus involves a combination of clinical evaluation, laboratory tests, and genetic testing. A water deprivation test can help differentiate between central and nephrogenic diabetes insipidus. Genetic testing can confirm mutations in the AQP2 gene.

Management

Management of nephrogenic diabetes insipidus focuses on maintaining adequate hydration and electrolyte balance. Thiazide diuretics, such as hydrochlorothiazide, may be used to reduce urine output. A low-salt, low-protein diet can also help manage symptoms. In some cases, nonsteroidal anti-inflammatory drugs (NSAIDs) may be prescribed to reduce urine volume.

Prognosis

With appropriate management, individuals with nephrogenic diabetes insipidus, nephrogenic type 3, can lead relatively normal lives. However, ongoing monitoring and treatment are necessary to prevent complications such as dehydration and kidney damage.

Also see

• Diabetes insipidus
• Antidiuretic hormone
• Aquaporin
• Nephron
• Genetic disorders