Endocrine Abstracts

JOINT937

Background: Severe hypercalcemia is a rare but serious condition in infants and children. It can present with symptoms such as hypotonia, poor feeding, vomiting, constipation, abdominal pain, lethargy, polyuria, dehydration, and seizures. The causes of hypercalcemia are categorized based on parathyroid hormone (PTH) levels. PTH-dependent hypercalcemia is characterized by elevated PTH, while PTH-independent hypercalcemia results from factors such as excessive production of parathyroid hormone-related protein (PTHrP) or 1, 25-dihydroxyvitamin D. PTHrP is a protein similar to PTH and can be secreted by certain tumors, including renal cell carcinoma, pheochromocytoma, and benign congenital mesoblastic nephroma. Hypercalcemia associated with PTHrP is rare, particularly in infants.

Case Presentation: A 5-month-old female, born at term with a normal pregnancy and delivery, presented to the emergency room with restlessness, constipation, and poor appetite. Routine lab tests revealed hypercalcemia (19 mg/dL), elevated ionized calcium (2. 43 mmol/l), and hypophosphatemia (3. 5 mg/dL). Further endocrine evaluation showed undetectable PTH levels, 25-hydroxyvitamin D at 37 ng/mL (normal range: 30-100), and low 1, 25-dihydroxyvitamin D at 27 pg/mL (normal range: 32-196). Urinalysis showed hypercalciuria (calcium/creatinine ratio of 2938 mg/gr). PTHrP testing was pending.

Management: Initial treatment included intravenous fluids, furosemide, calcitonin, and bisphosphonates, which normalized the calcium levels. Given the severity of hypercalcemia, hypophosphatemia, hypoparathyroidism, and low 1, 25-dihydroxyvitamin D3, malignancy was suspected as a cause of PTHrP secretion. Abdominal ultrasound demonstrated a renal mass. A subsequent CT scan of the chest, abdomen, and pelvis revealed a 53x51x69 mm lesion in the upper pole of the left kidney, along with five possible metastatic sites in the right lung. Left nephrectomy was performed, and biopsies of the renal lesion and lung metastasis confirmed the diagnosis of rhabdoid tumor of the kidney. Chemotherapy was initiated.

Conclusion: Although constipation and restlessness are often benign and common in infants, they can sometimes signal more serious underlying conditions, such as hypercalcemia. This case emphasizes the need to consider hypercalcemia in differential diagnoses and presents a rare cause—rhabdoid tumor of the kidney—as an underlying etiology.