ESPE Abstracts

Introduction: Parathormone-related peptide (PTHrP) regulates tissue calcium concentration by acting in paracrine or autocrine ways. It is mostly responsible for paraneoplastic hypercalcemia seen in adults. Paraneoplastic hypercalcemia in children is rarely reported in cancers such as ALL, medulloblastoma and hepatoblastoma (0.4–0.7%). In experimental studies, PTHrP is shown to be synthesized apart from neoplastic tissue (glomerulus and tubule cells).

Case: A five-month-old male patient was consulted to us by Pediatric Nephrology due to hypercalcemia. It was learned that he was born on 29^th gestational week as 1330 g, peritoneal dialysis was performed owing to bilateral renal hypoplasia, vitamin D prophylaxis was applied and thiazide diuretic or another medicine was never used. In physical examination, his height was determined as −3.32 SDS and weight was −3.8 SDS. There was no subcutaneous fat necrosis or skeletal dysplasia. The examination of other systems was normal. In laboratory workups, the following was seen; urea: 43 mg/dl (N, 10–38), creatinine: 3.0 mg/dl (N,0.4–0.7), Ca: 14 mg/dl (N, 8.8–10.8), P:2.3 mg/dl (N, 4–7), Mg: 2.5 mg/dl (N, 1.8–2.6), ALP: 1631 U/l (N, 82–383), PTH:6.64 pg/ml (N, 10–69), 25(OH)D₃:97 ng/ml (N, 20–100), 1,25 (OH)₂D_3: 60 pg/ml (N, 16.4–81), pH: 7.38 (N, 7.35–7.45) HCO3:24 mmol/l (N, 22–26). Hypothyrodism and adrenal insufficiency were ruled out. Echocardiography was normal. Primarily, in the etiology PTH independent hypercalcemia were thought with these findings. Vitamin D poisoning or CYP24A1 mutation was moved away in the patient with low phosphorus level, normal vitamine D metabolites. In direct radiograpies, Jansen’s Metaphyseal Dysplasia was not considered in the patient with no metaphyseal dysplasia or rickets finding. PTHrP level was determined as 5.9 pmol/l (<2.0). In the workups of bone marrow examination and imaging, no malignancy evidence was established. Due to hypercalcemia not responding to hydration and furosemide treatment, pamidronate infusion was applied. Serum calcium level returned to normal after pamidronate and hypercalcemia did not recur in clinical observation.

Conclusion: Although hypercalcemia related to PTHrP mostly emerge as paraneoplastic, it can be rarely seen in renal developmental pathologies. Hypercalcemia related to PTHrP should be thought in the differential diagnosis of cases followed up with hypoplasia/dysplasia and those in whom hypercalcemia has developed in their clinical observation.