Bartter's syndrome and erythrocytosis

We describe a patient, known since 1960, with Bartter's syndrome and erythrocytosis. The diagnosis was made on the basis of hypokalemic alkalosis, hyperplasia of the juxtaglomerular apparatus, resistance to the presser effect of angiotensin, extremely high plasma renin activity and normal blood pressure. This patient had a normal pattern of aldosterone excretion and a decreased ability of the kidneys to preserve potassium adequately. The nephropathy was characterized by a normal glomerular filtration rate, an irreversible inability of the kidney to concentrate the urine and a reversible inability of the kidney to excrete an acid load. The kidneys were enlarged; a biopsy specimen revealed hyperplasia of the juxtaglomerular apparatus, hyperplasia of the macula densa and an extensive fibrosis of the medulla. The intracellular red cell sodium level was elevated and the potassium level decreased during potassium depletion; they returned to nearly normal levels after adequate potassium supplementation. As a feature previously unknown in this syndrome the patient had a distinct erythrocytosis. There was an elevated red cell volume and an increase in the reticulocyte count after the oral administration of iron despite a high hemoglobin level. The erythropoietic activity of the serum, measured by bioassay, was increased to 10 times normal. We presume that there is a simultaneous overproduction of renin and erythropoietin in this patient with Bartter's syndrome. The stimulus for this over-production cannot be defined exactly. Our findings support the view that the primary defect in Bartter's syndrome is an impaired reabsorption of sodium in the ascending limb of Henle's loop. The case is further evidence for the juxtaglomerular apparatus being the production site of both renin and erythropoietin.