Cinacalcet treatment experience in hereditary vitamin D resistant rickets

BackgroundHereditary vitamin D resistant rickets (HVDRR) is a bone disorder characterized by a phenotype of rickets with onset at early stage of life with elevated alkaline phosphatase, hypocalcemia, hypophosphatemia, hyperparathyroidism and elevated levels of 1,25-dihydroxyvitamin D (calcitriol) as a consequence of the resistance of the vitamin D receptor (VDR). Mutations in the DNA-binding domain of the VDR of the vitamin D receptor have been characterized by a lack of response to traditional treatment with calcium and calcitriol. Secondary hyperparathyroidism and hypophosphatemia are the main factors in its pathogenesis. Cinacalcet is a calciomimetic drug that reproduces the action of calcium by increasing the sensitivity of the calcium-sensitive receptors (CASR) of the parathyroid glands that regulate the secretion of the parathyroid hormone (PTH).Case presentationWe describe its effectiveness and safety in a patient with HVDRR and review other published report cases in the literature. According to published experience, cinacalcet could be used as an adjunctive treatment for the HVDRR with mutations in the DNA-binding domain of the VDR refractory to traditional treatment. Due to lack of knowledge of possible effects of cinacalcet on CASR in the skeleton, long-term use should be avoided.ConclusionsThe optimal dose of cinacalcet for treatment of HVDRR ranges between 0.25 and 0.5 mg/kg/day. Serious side effects of cinacalcet have not been published in this type of patient, although we considered that a close monitoring is necessary in order to detect hypocalcemia.