Background Primary hyperparathyroidism (PHPT) is commonly associated with hypercalcemia, hypophosphatemia, and hypercalciuria. Hypokalemia and hypomagnesemia are rare and indicate a complicated etiology. Case presentation We describe a 74-year-old woman who presented with metabolic encephalopathy and moderate dehydration. Biochemical examinations revealed a parathyroid crisis with severe hypercalcemia (4.18 mmol/L), hypophosphatemia, hypokalemic (2.5 mmol/L) metabolic alkalosis, severe hypomagne