A serum potassium level above 10 mmol/l in a patient predisposed to hypokalemia.

BACKGROUND: A 58-year-old man, previously diagnosed with Bartter's syndrome, presented with a short history of vomiting, diarrhea and weakness. He had severe hyperkalemia (serum potassium levels >10 mmol/l), which was successfully managed. Post hoc investigation suggested that the patient had Gitelman's rather than Bartter's syndrome. INVESTIGATIONS: Physical examination, urine and blood analyses, chest radiography, electrocardiogram, renal ultrasound, and genetic analysis focusing on the SLC12A3 gene, which encodes the thiazide-sensitive Na/Cl cotransporter. DIAGNOSIS: Gitelman's syndrome and hyperkalemia secondary to acute renal failure plus exogenous potassium supplementation. MANAGEMENT: Intravenous calcium gluconate, insulin and dextrose administration. Temporary continuous venovenous hemodiafiltration. Genetic confirmation of the underlying molecular defect. Long-term treatment for Gitelman's syndrome with oral potassium and magnesium supplements and epithelial sodium channel-blocking drugs. Review of patient education regarding renal salt-wasting syndromes.