Bartter and Gitelman syndromes

What it is

Bartter and Gitelman syndromes are the hereditary hypokalemic tubulopathies, and both are autosomal recessive. Each behaves like a diuretic at a different site.

Bartter syndrome sits at the thick ascending limb of the loop of Henle, where the Na-K-2Cl cotransporter, NKCC2, is affected; it is the loop diuretic pattern, and frusemide is the drug named against it. Gitelman syndrome sits at the distal convoluted tubule, where the Na-Cl cotransporter, NCC, is affected; it is the thiazide pattern.

They are what is left when a patient with hypokalemia has a clear drug and nutrition history, no GI losses and a normal blood pressure, so the pathology is most likely tubular; RTA, distal and proximal, is the other name listed there.

How it presents

Bartter syndrome presents prenatally, in the neonate or in early infancy. Its concentrating ability is severely disturbed, so there is polyuria, and the listed features are severe polyuria, polydipsia, growth delay and hypotension.

Gitelman syndrome presents later, in late childhood or adolescence. Concentrating ability is normal or only slightly disturbed, and the listed features are muscle weakness, cramps and fatigue. Patients present similarly to those chronically using thiazide diuretics.

The blood pressure in both is normal or low. That is the point of contrast with Liddle syndrome, which also has hypokalemia and metabolic alkalosis but runs hypertensive.

Set out against each other the contrast runs as seven rows. Inheritance: AR in both. Localization: the thick ascending limb of Henle with the Na-K-2Cl co-transporter in Bartter, the distal convoluted tubules with the Na-Cl co-transporter in Gitelman. Diuretic-like: LOOP against thiazide. Age of presentation: prenatal, neonatal or early infancy against late childhood and adolescence. Concentration ability: severely disturbed, giving polyuria, against normal or slightly disturbed. Hypomagnesemia: 30% against always and significant. Urinary calcium: normal to high, that is hypercalciuria, against low, that is hypocalciuria. The age is the first of the seven to reach for, because it needs no laboratory at all: a patient first presenting in late childhood or adolescence is Gitelman, and one presenting before birth or in early infancy is Bartter.