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INTRODUCTION Hypocalcemia is characterized by abnormally low level of calcium in the blood. Normal reference range for calcium for children between 12- 19-year-old is 8.5-10.6 mg/dl . Severe hypocalcemia is considered as serum calcium level of <7 mg/dl and can present with tetany, seizures, and life-threatening cardiac arrhythmias. Etiology of hypocalcemia varies but hypoparathyroidism, pseudohypoparathyroidism and Vitamin D deficiency are some of the most common causes encountered by pediatrician endocrinologists. Association of rhabdomyolysis with hypocalcemia and elevated PTH is a rare presentation that should be considered, particularly for those children presenting with acute viral illness. We present a rare case of rhabdomyolysis associated with hypocalcemia not related to hypoparathyroidism. CASE A 12-year-old female presented to the emergency department with body ache, decreased oral intake and vomiting. She was found to be influenza positive. Electrolytes showed hypocalcemia (4.8 mg/dl). She subsequently had an undetectable 25-OH vitamin D level (<5 ng/ml) and elevated iPTH level (609 pg/ml). We discussed the possibility of her etiology of hypocalcemia to be Vitamin D deficiency although her presentation was atypical at an older age with a negative imaging for rickets, hyperphosphatemia (6.0 mg/dl), and normal alkaline phosphatase (334 unit/L). She also did not have any phenotypic features of Albright’s hereditary osteodystrophy and renal function was within normal limits. She was identified to have elevated creatinine kinase (4829 U/L) supporting rhabdomyolysis secondary to acute influenza as a cause of her hypocalcemia. Rhabdomyolysis, a known complication of influenza infection, causes cell membrane destruction which impairs the normal function of Na-K-ATPase channel. This leads to increase in intracellular sodium activating Na/Ca exchanger which in turn causes influx of calcium intracellularly causing hypocalcemia. Additionally, any injury or infection leads to high phosphorus release from cells due to cell lysis. High phosphorus is also caused by reduced oxidative metabolism in muscles impairing phosphate use. This excess of phosphate then combines with calcium and causes calcium-phosphate complex in soft tissues. Hyperphosphatemia also additionally inhibits 1 alpha hydroxylase limiting formation of calcitriol leading to hypocalcemia. CONCLUSION Our patient had severe hypocalcemia due to influenza-related rhabdomyolysis. Rhabdomyolysis is an important consideration as a cause of hypocalcemia in children, especially with acute viral illness. Accordingly, it is also important to obtain serum electrolytes in patients presenting with rhabdomyolysis as hypocalcemia may lead to complications like seizures and cardiac arrhythmia if not appropriately recognized and treated.


Endocrinology, Diabetes, and Metabolism | Pediatrics


Presented at ENDO 2024 (Annual Meeting for the Endocrine Society), June 1-4, 2024; Boston, MA.

Rhabdomyolysis As a cause of PTH independent hypocalcemia in a child with acute influenza infection