ESPE Abstracts

Background: Jansen’s Metaphyseal Chondrodysplasia is a rare autosomal dominant condition caused by activating mutations in the parathyroid hormone/parathyroid hormone related peptide receptor (PTH1R). It is associated with persistent PTH-independent hypercalcemia and hypercalciuria from an early age. Our patient, a 2 year old boy with genetically proven Jansen’s Metaphyseal Chondrodysplasia, developed bilateral medullary nephrocalcinosis secondary to persistent hypercalciuria. A single previous case report noted improvement in hypercalciuria in an adult patient with bisphosphonate therapy.

Objective and hypotheses: Bisphosphonates are a well-recognised treatment for hypercalcemia due to malignant and non-malignant bone disorders. We posited that intravenous bisphosphonate administration would improve serum and urine calcium concentrations, and potentially halt progression of nephrocalcinosis.

Method: Our patient received three intravenous infusions of Pamidronate disodium over a five month period – 0.25 mg/kg at 0 months, 0.5 mg/kg at 1 month, and 0.5 mg/kg at 5 months, in combination with a low calcium diet. The infusions were administered in hospital according to local protocol. Serum and urine calcium and phosphate were measured at baseline and following treatment

Results: There was no appreciable improvement in serum or urine calcium concentrations following pamidronate infusion. Serum alkaline phosphatase also remained mildly elevated. The degree of nephrocalcinosis was also unchanged. Intravenous bisphosphonate in combination with low calcium diet was not successful in decreasing chronic hypercalcemia or hypercalciuria in our patient.