SAT-821 - Uso De Cinacalcet En Hiperparatiroidismo Secundario A Raquitismo Hipofosfatemico Hereditario

Introduction: X-linked hypophosphatemic rickets (XLH) is a rare disease caused by variants in the PHEX gene.Secondary and tertiary hyperparathyroidism have been described in these patients; among the possible causes are treatment with phosphate salts, deficient calcitriol production due to excess FGF23, and parathyroid resistance to the action of FGF23.
We present the case of a patient treated with burosumab plus calcitriol for the management of hyperparathyroidism secondary to XLH.
A 20-year-old patient has been under follow-up since birth for X-linked hypophosphatemic rickets. His mother, grandmother, and maternal aunt all have the same condition. He began conventional treatment with phosphate salts and calcitriol until age 11. From birth, the patient presented with elevated PTH levels and calcium levels at the upper limit of normal. He started burosumab 0.8 mg/kg subcutaneously every 14 days with clinical success, correction of bone deformities, improvement in pain, and school attendance appropriate for his age. He began participating in sports. At age 17, he began the transition process, during which an increase in calcium and PTH levels was observed. He weighed 66 kg, was 154.7 cm tall, and a renal ultrasound revealed mild nephrocalcinosis. The burosumab dose was reduced to 50 mg/kg every 28 days. Calcium levels stabilized until age 20, at which point they began to rise again. Initiate cinacalcet 30 mg orally every 12 hours.
2005 2008 2018 2021 2023 2024 2025
Calcium (8.2 a 10.3 mg/Dl) 10.1 10.5 11.2 10.4 9.5 10.7 9.7
Fosfato
(2.5-4.5 mg/Dl) 3.1 2.6 2.3 3.7 2.5 2.1 2.9
PTH (15-65 pg/ml) 70 140 218 156 153 209 103
Vitamina D ng/ml 19 43 25 32

1,25 (OH)2D: 52 y 65.1 pg/mL (19.9-79.3)

Conclusion:
The prevalence of secondary and tertiary hyperparathyroidism was 25% and 10% respectively in XLH2. Evaluation of the parathyroid axis is necessary from the time of diagnosis of the disease, as well as its treatment, to avoid associated complications.
Treatment with cinacalcet in combination with burosumab minimized the risk of hypercalcemia and nephrocalcinosis and prolonged the time on medical treatment until parathyroid surgery.

1) Carpenter TO, Insogna KL, Zhang JH, Ellis B, Nieman S, Simpson C, et al.
Circulating Levels of Soluble Klotho and FGF23 in X-Linked Hypophosphatemia:
Circadian Variance, Effects of Treatment, and Relationship to Parathyroid Status.
The Journal of Clinical Endocrinology & Metabolism. 2010;95(11):E352-7, doi:
10.1210/jc.2010-0589.
2) Lecoq A-L, Chaumet-Riffaud P, Blanchard A, Dupeux M, Rothenbuhler A, Lambert
B, et al. Hyperparathyroidism in Patients With X-Linked Hypophosphatemia.
Journal of Bone and Mineral Research. 2020;35(7):1263-73, doi:
10.1002/jbmr.3992.

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