Endocrine Abstracts

Introduction: Hypophosphatemic rickets comprehends a group of hereditary diseases characterized by hypophosphatemia and defective bone mineralization. The most common form is X-linked, with a prevalence of 1:20.000.

Objectives: Describe the follow up of patients with hypophosphatemic rickets in a public center in Brazil.

Methods: Patients with hypophosphatemic rickets were selected from a database of Endocrinology and Metabolism Service of Paraná (SEMPR). Medical records were revised to collect clinical and laboratory evaluation.

Results: Twenty-two patients were included, being 15 women. The median follow up was 11 years (1 month – 27 years), with a median age at diagnosis of 105 months (13 – 384 months). All patients presented with bone deformity, 11 (50%) patients with genus varus, 10 (45%) patients with genus valgus and 1 (4%) patient with both. Other bone deformities present were: 6 (27%) lordosis, 6 (27%) scoliosis, 5 (22%) bone deformity with frontal bossing and 12 (54%) epiphyseal enlargement. Median initial laboratory results were as follows: calcium 9.1 mg/dL (8.3–9.9 mg/dL), phosphorus 2.18 mg/dL (1.3–3.0 mg/dL), alkaline phosphatase 848 U/L (19.26–2109 U/L), parathormone 122 pg/mL (6–523 pg/ml), total reabsorption of phosphorus of 43%. Initial X-rays showed 12 (54%) patients with typical rickets findings, 3 (13%) patients with reduced bone mineral density and 2 (9%) patients with fractures. Fanconi syndrome was diagnosed in 5 (22%) patients. Treatment consisted of phosphorus supplementation in 14 (63%) patients with a median dose of 1.7 gr/day, calcitriol in 13 (59%) with a median dose of 0.32 mcg/day and combined treatment in 9 (40%). During follow up showed fractures in 8 (36%) patients, most frequently in femur (7) 41% and tibia (4) 23%. Eight patients were evaluated DEXA and all of them showed increased BMD in all sites. Nine patients were evaluated with hand x-ray for bone age and all showed with delay, with a median of 19 months (12-84 months). Alkaline phosphatase after treatment went down to a median of 236 U/L (decrease of 72%) and creatinine went up by a median of 37%. Calcium, phosphorus and parathormone didn’t show significant alterations. Kidneys were assessed by ultrasonography in 17 (77%) patients, and showed nephrocalcinosis and nephrolithiasis in 3 (17%) and renal parenchymal disease in 4 (23%). Secondary hyperparathyroidism was observed in 1 (4%) patient.

Conclusion: Phosphorus and calcitriol induced bone mineralization leading to symptom improvement and increased bone mineral density. Then, overtreatment could possibly lead to renal complications, as shown in 40% of patients.