Use of cinacalcet during pregnancy in hypophosphatemic vitamin d resistant rickets with tertiary hyperparathyroidism

Cinacalcet is used to treat tertiary hyperparathyroidism in renal failure. However, its use in pregnancy and hereditary hypophosphatemic vitamin D resistant rickets (HVDRR) has not been reported. In this study we describe the use of cinacalcet in a case of HVDRR with tertiary hyperparathyroidism diagnosed during pregnancy, in a tertiary care hospital in an academic center. A 29 year old woman with HVDRR was found to have tertiary hyperparathyroidism at week 15 of her second pregnancy: serum calcium 11.4 mg/dL, intact parathyroid hormone 307 pg/mL. Reductions in potassium phosphate and calcitriol were unsuccessful in restoring normocalcemia. Cinacalcet was started to avoid parathyroidectomy and to reduce the risk of hypercalcemia to the mother and fetus. After 10 weeks of treatment, calcium normalized but placental abruption prompted delivery at week 27 of gestation. A healthy live male was born with weight of 964 g and serum calcium of 9.0 mg/dL. After delivery cinacalcet was stopped. Eight months later, calcium was 10.0 mg/dL and intact parathyroid hormone 426 pg/mL. This case demonstrates the successful use of cinacalcet during pregnancy to manage hypercalcemia in a patient with HVDRR and treatment related tertiary hyperparathyroidism.