Gitelman's syndrome is genetically distinct from other forms of Bartter's syndrome

In the past the term Bartter's syndrome has been used to describe a spectrum of inherited renal tubular disorders with hypokalemic metabolic alkalosis and overlapping and additional clinical and biochemical features. Pathogenesis remained uncertain until recently Gitelman's syndrome, the hypokalemic-hypomagnesemic variant with hypocalciuria, was linked to the gene encoding the thiazide-sensitive Na-Cl-cotransporter (TSC) located on chromosome 16q. Various mutations in the TSC gene were identified in patients with Gitelman's syndrome. To clarify whether different forms of hypokalemic tubular disorders (HTD) represent variable phenotypes of a common genetic defect, we performed linkage analyses in 17 families with different symptoms of HTD with four highly polymorphic chromosome 16 DNA markers closely linked to the TSC gene. Linkage of Gitelman's syndrome to the TSC locus was confirmed in our families with a maximum two-point Lod score Z = 4.70 (θ = 0.001) for marker locus D16S526. Highly negative LOD scores were obtained at this locus in our families with classic Bartter's syndrome (Z = -9.89, θ = 0.001) and hyperprostaglandin E syndrome (Z = -11.24, θ = 0.001). Our data prove that Gitelman's syndrome is genetically distinct from classic Bartter's syndrome and hyperprostaglandin E syndrome. It remains unknown if classic Bartter's syndrome and hyperprostaglandin E syndrome are caused by a common genetic defect.