Classic Bartter syndrome
Classical Bartter syndrome is an autosomal recessive disease, which occurs in infancy. Its symptoms consist in hypokalemia, alkalosis, secondary hyperaldosteronism and hypotension due to renal salt wasting.
This subtype of barter-syndrome almost represents the 2 cases originally described by Bartter in 1962.
Prevalence as in all salt wasting tubulopathies is not exactly determined. It is assumed between 1:50,000 and 1:100,000.
The clinical picture is variable. Early onset with life-threatening hypokalemia and hyponatremia is possible as well as mild cases that are only revealed by family screening. Usually, manifestation happens in infancy. Patients fail to thrive and show electrolyte disturbances. Sometimes, besides hypokalemia and hyponatremia, low plasma magnesium levels can be measured. Renal calcium excretion is only slightly altered, so nephrocalcinosis is rare.
Because hypokalemia and alkalosis are present in various salt-wasting disorders, diagnosis predominantly relies on ruling out Gitelman syndrome and the other types of Bartter syndrome. Molecular genetic analysis is of particular help, especially in uncertain cases with mixed clinical symptoms and a possibly compound heterozygous genotype.
Gitelman syndrome and the other types of Bartter syndrome are the main differentials. Age of onset, serum magnesium levels, urine excretion of calcium and prostaglandins along with a therapeutic trial with indometazine might be particularly helpful in differentiating.
The disease is caused by loss-of-function mutations in chloride channel B, which is located in the thick ascending limb of the loop of Henle.
BARTTER FC et al. (1962) Hyperplasia of the juxtaglomerular complex with hyperaldosteronism and hypokalemic alkalosis. A new syndrome.[^]