Diabetes insipidus, nephrogenic affects the normal fluid balance of the body and the kidneys produce dilute urine in large quantity. As the result, the affected individuals are excessively thirsty and become dehydrated particularly in hot weather. This condition can develop as an acquired form or can be hereditary. The acquired form is caused by various illnesses or as the result of certain medications. The hereditary condition occurs by genetic mutations which become apparent in the initial few months of the infant’s life.
Causes
The hereditary form is identified to be caused by two genetic mutations; the AVPR2 accounting for 90% of the cases and AQP2 gene accounts for the 10%. Both the genes are essential for the production of a protein that regulates the quantity of water to be retained and excreted by the body. The hormone known a vasopressin or antidiuretic hormone (ADH) is essential in regulating the balance of fluid intake and the excretion as urine. The mutation in the gene prevents the kidneys from functioning to signals from the ADH. In the acquired form of this disorder, the condition may be caused by various chronic kidney disease, certain medications, hypercalcemia (excess calcium in the blood) or the obstruction of the urinary tract. As the result, the kidneys are unable to respond to the ADH effectively thus impairing the reabsorbing of water by the body causing the excessive quantity of urine.
The inherited form of this condition can occur as an X-linked recessive pattern when the mutation in the gene AVPR2 is identified. This develops in one of the sex chromosomes and as the males only have one copy of the X chromosome, they are likely to develop this condition. When the mutation in the AQP2 is detected, the inheritance pattern can either be an autosomal dominant pattern where one copy of the defective gene is sufficient to cause this disorder or can be an autosomal recessive trait when both the copies of the genes contain the mutation.
Symptoms
The symptoms of this condition can vary from person to person. Usually, the acquired form is less severe than the inherited condition which is apparent shortly after the birth. The symptoms of diabetes insipidus, nephrogenic is the excessive thirst and excessive urination that can also occur at night. The symptoms in infants include vomiting, tiredness, irritability, unexplained fever, diarrhea, poor feeding and as the result poor weight gain or growth. Signs of dehydration can include weakness, dry mucous membranes, weight loss and dry skin. Dehydration among the infants is a serious condition and if left untreated complications can develop such as seizures, mental disabilities and developmental delays.
Diagnosis
The diagnosis is based on the features that are associated with this condition such as excessive thirst and urination. Additional clinical tests can include blood and urine samples to determine the osmolality that evaluates the proportions of solids in relation to water in the blood and urine. A water deprivation test involves the individual not taking any fluids for a specific period of time and the urine sample is evaluated for levels of vasopressin. Additional tests can include CT scan, MRI image and ultrasound to detect any abnormalities of the kidney and the brain.
Treatment
The treatment is focused on taking sufficient fluid intake to prevent dehydration and to reduce the urine output. Addition of specific diet such as low sodium and medications can decrease the urine output. The acquired form of this condition requires the treatment of the underlying cause which can reverse the problem but may take several weeks.
References
https://rarediseases.org/rare-diseases/nephrogenic-diabetes-insipidus/
https://medlineplus.gov/ency/article/000511.htm
https://ghr.nlm.nih.gov/condition/nephrogenic-diabetes-insipidus#genes
