What is Antenatal Bartter Syndrome ?
In contrast to Classic Bartter Syndrome and Gitelman Syndrome, the Antenatal variant of Bartter Syndrome has both the features of metabolic alkalosis (from the low potassium), as well as profound systemic manifestations. Out of all of the variants this form is the most severe.
Antenatal Bartter Syndrome is characterized by polyhydraminos (Increased water in the uterus) due to polyuria in utero (Which means the fetus has urinated so much it has led to an increase in the fluid in the uterus. For this reason the infant is usually born premature.
After birth, life-threatening episodes of fever and dehydration occur secondary to profound polyuria (Increased urination), vomiting, and diarrhea.
Severe electrolyte imbalances and marked growth retardation are typical which basically means that this infants are very small for their age from the loss of much needed electrolytes and from being premature. With the complication of them already being premature it is difficult to get these children to grow. But with early diagnosis and treatment these children do well.
The majority of these infants also suffer with severe hypercalciuria (High urine calcium) with associated nephrocalcinosis (Formation of calcium deposits in the kidneys) and osteopenia (reduction in bone volume).
These infants also have an abnormally high level of prostaglandin E2 production.
Cyclooxygenase inhibitors,eg, Indomethacin, have been shown to reverse all the clinical and laboratory derangements, save for those related to calcium homeostasis.
In past literature it was noted that these children came from marriages in which the parents were relatives (First Cousins), We now know this is not true. It is also documented in the literature that these children have a particular characteristic face (Drooping mouth, prominent forehead, large ears and triangular shaped face). We know this is not true either. This was noted in a particular group of ethnic population.
What are the Symptoms?
- Polyhydramnios (Increased water in the uterus during pregnancy)
- Hypercalciuria (Increased Calcium in the urine)
- Delayed Growth
- Increased prostaglandin excretion
- Polyuria (Increased Urination)
- Severe Electrolyte Imbalances
- Growth Retardation
- Severe Hypercalciuria
- Nephrocalcinosis (Calcium deposits on the kidney)
- Osteopenia (Decreased Bone Density)
What are the treatments?
Therapies designed to arrest or correct the primary defects are not yet available. Therefore, the main therapeutic objective is to ameliorate the hypokalemic, hypochloremic, metabolic alkalosis. Potassium chloride supplementation is the mainstay of therapy. Oral supplementation alone is usually ineffective, however, in normalizing serum potassium concentrations, probably because large amounts of exogenous potassium further stimulates aldosterone synthesis with resultant increases in hyperkaliuria (potassium in the urine). The addition of potassium-sparing diuretics, eg, spironolactone, amilioride, or triamterene, may help to correct the total body potassium balance. In fact, the therapeutic combination of the potassium supplementation and potassium-sparing diuretics has been associated with increased growth rates in affected children. In young infants, marked urinary salt wasting may also occur and necessitate Sodium Chloride supplementation. Indomethacin therapy ameliorates many of the clinical and biochemical abnormalities in Antenatal Bartter Syndrome. In fact, indomethacin therapy has been shown to attenuate the systemic symptoms, eg, fever, vomiting, diarrhea; improve growth; and ameliorate the aldosterone-induced salt wasting and hypokalemia. Given that activation of the renin-angiotensin-aldosterone axis drives both urinary potassium wasting and stimulation of prostaglandin production, numerous investigators have used angiotensin-converting enzyme inhibitors in treating Bartter syndrome patients. While variable success has been noted, some patients have had significant biochemical improvement and symptomatic relief with Captopril. The major limitation of this therapy is the development of symptomatic hypotension, because blood pressure maintenance in this population is largely dependent on angiotensin II.
What is the Prognosis?
The limited prognostic information available suggests that early diagnosis and appropriate treatment of infants and young children with Classic Bartter Syndrome and the Antenatal variant may improve growth and development. On the other hand, sustained hypokalemia and hyperreninemia can cause progressive tubulointerstitial nephritis, resulting in end-stage renal disease.Print This Post