Bartter syndrome is a group of related kidney disorders that cause imbalances of sodium, chloride, potassium and other electrolytes in the body. Bartter syndrome is inherited and can affect the baby even while it’s in the womb by increasing the volume of amniotic fluid. This condition, called polyhydramnios, can cause the baby to be born prematurely. The syndrome is caused by defects in different genes. It is a rare disorder, and about one million people are thought to be affected by it worldwide. It affects boys and girls equally and is incurable.
Definition & Facts
A baby who is born with Bartter syndrome often fails to thrive because they lose too much salt in their urine. This makes them dehydrated while increasing their urine output. They can also become constipated.
They also lose a great deal of calcium and potassium. The calcium causes their bones to grow weak while the potassium causes their muscles to become weak. Calcium can also accumulate in the kidneys and harden them. Loss of potassium leads to fatigue and muscle cramping. Some Bartter syndrome children have hearing loss because their auditory nerves are impaired and can’t send signals to the brain.
Patients may also have low blood levels of chloride while having alkaline, renin and aldosterone levels that are too high. Aldosterone helps the body conserve salt, while renin is part of a system that regulates blood pressure.
Types I, II and IV Bartter syndrome can pose a danger to an unborn baby’s life. Type III Bartter syndrome begins in childhood and is generally less severe than the others. Type IV is the type of Bartter syndrome that’s connected to hearing loss. Some health care professionals divide Type IV into IVa and IVb.
Symptoms & Complaints
In classic Bartter syndrome, the child suffers cramps, weakness, vomiting, fatigue, malaise, and fevers. They are constantly thirsty and have a constant urge to urinate, especially at night. This need to urinate is such that the child can become dehydrated even when they drink a great volume of fluids. They may also crave salt, may not grow as well as they should, and may be shorter than other adults when they are fully grown. They may also suffer developmental delays.
Babies who are born with the syndrome also urinate a great deal and can be at risk for life-threatening fevers and dehydration. The risk of dehydration is exacerbated by diarrhea and vomiting. Some babies born with Bartter syndrome have unusual features such as a triangular face, pointed ears, large eyes and a protruding forehead.
The imbalance in electrolytes can also lead to heart problems, including cardiac arrhythmias. Some Bartter syndrome patients are at risk for sudden death. The build-up of calcium in the kidneys can lead to kidney stones and may damage the kidneys.
Bartter syndrome is caused by genetic mutations. So far, medical researchers have discovered genes whose mutations give rise to the different types of the syndrome. These genes are the SLC12A1, KCNJ1 CLCNKB, and BSND genes.
Type IV Bartter syndrome can arise as a result of mutations of BSND or mutations found in both the CLCNKA and CLCNKB genes. All of these genes help the kidney function normally, and the mutations do not allow the kidneys to reabsorb salt the way they should. Because of this, too much salt is excreted in the urine. The loss of salt impairs the reabsorption of potassium, calcium and other ions.
A copy of the defective gene must be inherited from both parents for the child to develop Bartter syndrome. This is called an autosomal recessive pattern. Rarely, there is a Bartter syndrome patient who does not have these specific genetic defects. Researchers are searching for other genes that can cause the condition.
Diagnosis & Tests
Doctors diagnose Bartter syndrome by taking the patient’s medical history, checking their symptoms and running tests. These include evaluating the levels of electrolytes in the blood. Clinical urine tests are given to determine the electrolyte levels in the urine and to find prostaglandin E2. The levels of this compound are elevated in Bartter syndrome and cause the excess production of urine. The doctor may order an ultrasound of the patient’s kidneys.
If the fetus is suspected of having Bartter syndrome, the amniotic fluid can be tested for high levels of aldosterone and chloride. Genetic testing can give a sure diagnosis of Bartter syndrome, but labs who perform these tests are specialized.
Treatment & Therapy
The treatment of Bartter syndrome needs to be tailored to the individual patient. Specialists may need to work as a team to treat the patient, including doctors who specialize in the functioning of the kidney, social workers and psychologists.
The goal of treatment is to make sure that the fluids and electrolytes in the patient’s body stay in balance. This may require supplementation with potassium chloride. Newborn babies may need to be hydrated with saline solution via a catheter in the vein. At the same time, health providers must be sure that this treatment doesn't worsen the baby’s constant need to urinate. This can be eased with prostaglandin antagonists.
All of these drugs need to be carefully monitored because of side effects such as dangerously low blood pressure and damage to the heart and kidneys. Patients need to take in salt and water, eat foods rich in potassium and take calcium and magnesium supplements. Caregivers must be especially vigilant with patients with Bartter syndrome if they are subject to stresses such as disease or surgery, since stress affects electrolyte levels.
Prevention & Prophylaxis