Chronic metabolic alkalosis with poliuria and hypo-electrolytemia of renal origin, associated with low to normal blood pressure, despite elevated plasma renin activity and aldosterone levels, and preserved glomerular function. This subtype of Bartter´s syndrome is also characterized by reduced plasma levels of calcium and magnesium and autosomal dominant inheritance.
Affected patients have a familial history of seizures. Symptoms begin after birth with hypocalcemic seizures and hypoparathyroidism. Patients exhibit some of the clinical features of Bartter´s syndrome such as thrist, polyuria, renal salt loss, and weakness.
Metabolic alkalosis with hypocalcemia and hypomagnesemia associated with decreased hypoparathyroid hormone and increased plasma level of phosphate. Characteristically urinary levels of calcium and magnesium are elevated, and patients usually develop nephrocalcinosis. Polyuria and renal salt wasting are present, but plasma potassium level is normal.
Bartter´s syndrome type V is caused by severe gain-of-function mutations in the extracellular Ca++ -sensing receptor (CasR), which is highly expressed in the basolateral membranes of the ascending limb of loop of Henle, and inhibits salt transport through ROMK inhibition, resembling Bartter´s syndrome type II. Further, overly active CaRs in the parathyroid and in the thick ascending limb of Henle’s loop to decrease urinary Ca reabsorption and those in collecting duct to inhibit vasopressin action, giving rise to inappropriate hypercalciuria and water loss, respectively. The pattern of inheritance is autosomal dominant. For the genetic study it will be necessary samples of the index case and the parents.
Treatment is based on electrolyte and water supplementation, and thiazide diuretics to reduce urinary Ca excretion and thereby permit serum Ca to increased to nearly normal levels without hypercalciuria. Treatment with active vitamin D metabolites should be reserved for symptomatic patients.
Permanent hereditary disease with favorable outcome and prognosis if treated.
Treatment with vitamin D to correct the hypocalcemia may lead to more severe hypercalciuria, nephrocalcinosis, and renal impairment.