(1533) Calcium-Alkali Syndrome due to Calcium Carbonate Use in a Lung Transplant Recipient

Introduction: Calcium-alkali syndrome (CAS), also known as milk-alkali syndrome (MAS), is typically characterized by hypercalcemia, acute kidney injury, and metabolic alkalosis. Initially reported in 1923 following the Sippy regimen, CAS is a resurgent cause of hypercalcemia following hyperparathyroidism and malignancy. We present a case of CAS in a lung transplant recipient due to prolonged use of calcium carbonate and calcitriol.

Description: A 52-year-old man with cystic fibrosis underwent bilateral lung transplant complicated by chronic rejection, CKD stage 4, and GERD. He presented with fatigue, chest discomfort, and increased muscle spasms with slower cognition for the prior few days. Labs revealed severe hypercalcemia with elevated levels of calcium (14.9 mg/dl, ionized calcium (7.29 mg/dl) and creatinine (3.85 mg/dl with abaseline around 2.7 mg/dl), and metabolic alkalosis The patient reported taking calcium carbonate 600 mg frequently for the week prior to presentation for worsening gastric reflux symptoms in addition to tacrolimus and calcitriol. EKG was noted with mildly reduced qT interval. Aggressive IV fluid resuscitation with calcitonin was initiated with adequate response. The patient’s presenting symptoms and lab abnormalities resolved at discharge. Work-up for secondary causes remained negative.

Discussion: Primary hyperparathyroidism and malignancy account for most hypercalcemia cases, and CAS has reemerged as the third leading cause. CAS classically presents with a triad of hypercalcemia, metabolic alkalosis, and renal injury. In the current case, CAS resulted from routine use of antacids or calcium supplements for treatment of GERD or osteoporosis prevention. In patients with predisposing factors - as in the case of this immunocompromised patient on tacrolimus, TUMS, and calcitriol - doses lower than the daily limit of 2 g may result in CAS. It is important to consider CAS when working up hypercalcemia to prevent further recurrence and undergoing expensive, time-consuming workups for hyperparathyroidism and malignancy. The exact mechanism for development of CAS remains unclear, and it can lead to permanent injury and more serious complications of hypercalcemia, but early recognition can quickly reverse potential adverse effects.