Session: SAT 199-223-Disorders of Bone & Calcium Homeostasis: Case Reports
Poster Board SAT-208
Hypophosphotemic rickets (HR) is a caused by a number of genetic mutations resulting in decrease reabsorption of phosphorus by the proximal renal tubule along with inhibition of 1α-hydroxlase leading to low levels of 1,25 (OH)2-vitamin D. Current standard treatment includes phosphate replacement and 1,25 (OH)2-vitamin D. Complications to this therapy include renal insufficiency, and secondary hyperparathyroidism. Calcimimetics have been introduced in management as it modulates the calcium sensing receptor (CaR) resulting in decrease of parathyroid hormone (PTH) secretion and lowering phosphorus product.
Two cases of patients with HR had been managed with phosphorus replacement and calcitriol, but serum phosphorus levels were hard to normalize even on high doses of phosphorus replacement. Cinacalcet at 30 mg twice daily was started, and serum measurements of calcium, phosphorus, and PTH was compared before starting and after 1week treatment.
Case 1 is an 11yo boy who presented at our clinic at 7yrs of age with history of leg bowing and sleep apnea due to facial bone malformation, dental caries, and bone pain. Patient was shown to have X-linked hypophosphatemic rickets with confirmed missense mutation of PHEX gene. On calcitriol 1.5mcg daily and phosphorus 30mg/kg/day divided in 4 doses phosphorus was never above 2.5mg/dL, while PTH was 70pg/dL and Calcium of 9.6mg/dL. One week after starting cinacalcet, phosphorus improved to 3.1 along with a decrease in PTH to 12 and calcium of 9.
Case 2 is of a 6yo girl who presented at 2yrs of age with leg bowing, frontal bossing, and bone pain. Genetic analysis for cause of HR pending. Patient was on calcitriol 1mcg daily along with phosphorus 18mg/kg/day divided in 4 doses. Cinacalcet was started and one week later phosphorus improved from 2.6 to 3.5, PTH went from 20 to 12, while calcium changed from 9.3 to 9.1.
Addition of cinacelcet to Phosphorus and Calcitriol had an immediate effect on decreasing phosphorus replacement requirements along with reduction in PTH levels. Thus calcimimetics such as cinacalcet can play a quick and significant role in better managing disease process of HR and its sequelae.
Nothing to Disclose: AP, DK, APSB, SBT
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