An Atypical Case of Primary Renal Tubular Hypokalaemic Metabolic Alkalosis with Chronic Tophaceous Gout

Abstract

A 55-year-old woman was referred to our ward for further evaluation of marked hyperuricaemia and suspected tophi. On physical examination, huge subcutaneous nodules were observed on the knee joints as well as a small nodule on the lateral side of the left sole. Blood chemistry showed marked hyperuricaemia (0.85 mmol/l), hypokalaemia (2.7 mmol/l) and a mild degree of renal insufficiency. Arterial blood gas analysis showed signs of metabolic alkalosis. Daily urinary uric acid excretion on a purine non-restricted diet was 8.9 mmol/day. Uric acid clearance and fractional uric acid clearance were 0.8 ml/min and 2.6%, respectively. Plasma renin activity was 21.8 ng/ml/h, and plasma angiotensin II and aldosterone concentrations were 61 and 121 pg/ml, respectively. However, pressor response to an intravenous administration of angiotensin II was normal. The urinary calcium to creatinine molar ratio was 0.069, and serum magnesium concentration was normal to supranormal. A biopsy of the subcutaneous nodule showed a typical appearance of tophus. Based on these findings, the patient was diagnosed with an atypical case of renal tubular hypokalaemic metabolic alkalosis, with marked hyperuricaemia and tophi as the initial manifestations. So far, only four cases of Bartter’s syndrome with gout and/or hyperuricaemia have been described in Japan. This rare case is presented and its mechanism of hyperuricaemia discussed.