MON-258 Toddler with Hypercalcemia: Diagnosis of Familial Hypocalciuric Hypercalcemia

Introduction: Hypercalcemia has a wide range of causes, and there are many important diagnostic values that must be considered by the pediatrician in reaching a diagnosis. Case and Discussion: This case provides an example for the outpatient-workup of hypercalcemia in pediatric population. The patient is a 17 m/o male with a three month episodic history of non-bloody, watery diarrhea and poor weight gain. He was born at 39 weeks gestation to a G2P2 mother. The pregnancy was complicated by DM-II and obesity. All newborn screening was normal. Initial testing revealed an elevated serum calcium level of 11.0mg/dL. In the initial workup of pediatric hypercalcemia, it is important to establish the presence of an appropriate physiologic response to elevated serum calcium. In patients with functional parathyroid glands, hypercalcemia should induce a low or suppressed level of parathyroid-hormone (PTH) secretion. N appropriate response suggests that the underlying cause of hypercalcemia is PTH-independent, such as hypervitaminosis D, sarcoidosis, or paraneoplastic secretion of PTHrp. If PTH levels are elevated, PTH-dependent causes of hypercalcemia must be considered, such as 1º/3º hyperparathyroidism and familial hypocalciuric hypercalcemia (FHH). Random urine calcium levels are useful in distinguishing between these causes, as calcium reabsorption in the kidney will hit a saturation point with 1º/3º hyperparathyroidism, resulting in detectable calciuria. Further testing in this patient revealed serum electrolytes, albumin, total protein, creatinine, and LFTs all within normal limits. PTH levels were elevated at 99.7 mg/dL, suggesting a PTH-dependent cause of hypercalcemia. Random urine calcium was collected and found to be significantly low at <1.0mg/24h, which suggests a diagnosis of FHH. The patient was referred to a radiologist for ultrasound of the neck to effectively rule out neoplastic-related 1º hyperparathyroidism. Conclusion: Evaluation of hypercalcemia is important and relevant to rule out parathyroid or other diseases. FHH is normally asymptomatic, and there are no curative treatments for this condition.