ESPE Abstracts (2018) 89 RFC11.2

aDepartment of Pediatric Endocrinology, Ankara University School of Medicine, Ankara, Turkey; bMarmara University, Istanbul, Turkey; cDokuz Eylül University, İzmir, Turkey; dIstanbul University, Istanbul, Turkey; eSBU Gazi Yasargil Education and Research Hospital, Diyarbakır, Turkey; fSamsun Ondokuz Mayıs University, Samsun, Turkey; gUludağ University, Bursa, Turkey; hErciyes University, Kayseri, Turkey; iKonya Education and Research Hospital, Konya, Turkey; jSami Ulus Children Hospital, Ankara, Turkey; kNecmettin Erbakan University, Konya, Turkey; lAnkara Child Health and Haematology Oncology Hospital, Ankara, Turkey; mKartal Dr Lufi Kırdar Hospital, Istanbul, Turkey; nEge University, İzmir, Turkey; oSBU Adana Numune Hospital, Adana, Turkey; pDicle University, Diyarbakır, Turkey; qFırat University, Elazığ, Turkey; rDiyarbakır Children Hospital, Diyarbakır, Turkey; sGülhane Education and Research Hospital, Ankara, Turkey; tErzurum Regional Education and Research Hospital, Erzurum, Turkey; uTrakya University, Edirne, Turkey; vEskisehir Osman Gazi University, Eskisehir, Turkey; wAydın Adnan Menderes University, Aydın, Turkey; xKatip Çelebi University, İzmir, Turkey

Aim: Hypophosphatemic rickets (HR) is a rare renal phosphate wasting disorder commonly related to X-linked form, caused by PHEX mutations and it treatment and follow-up is challenging due to imperfect treatment options. Here we presented nationwide data on HR with initial and follow-up data on the patients presented to the pediatric endocrinology clinics before the age of 18 years.

Results: From 24 centers, 158 patients (93 male/65 female) were included in the study data. The patients features at presentation has been given in the table. Genetic analysis (n:75) showed PHEX mutation in 80% and DMP1 in 4%, SLC34A3 in 3%, CLCN5 in 1.3% patients. The mean follow-up period of the patients was 6.7±2.4 years. First 3 year treatment response could be evaluated for 91 patients and, mild increase in P (from 2.6±0.6 to 2.7±0.6, 2.8±0.7 and 2.8±0.7 mg/dl), decrease in ALP (from 786±522 to 627±449, 561±319 and 546±327 U/l) and, elevation in PTH levels (from 68±48 to 84±77, 79±66 and 93±99 pg/ml) had been detected (from intitial to 1st, 2nd and 3rd year, respectively). The height SDS were −2.38, −2.77, −2.72, −2.47 at intitial, 1st, 2nd and 3rd year of treatment, respectively (P>0.05). In follow-up: 36% of the patients showed complete or partial improvement in leg deformities, and, these patients had worse tubular phosphate resorption (70% vs 77%, P: 0.046), better height SDS and ALP at presentation and following years with similar phosphate levels at presentation with better levels in 1st (2.9 vs 2.6) and 2nd years (3.0 vs 2.7) of treatment, even the treatment doses of phosphate were similar, however, higher calcitriol doses in 1st and 3rd years in improved group. Furthermore, 27 patients (17%) developed nephrocalcinosis (NC), the patients showed no difference in biochemical differences in presentation and follow-up, but 3rd year PTH was higher (145 vs 78 pg/ml, P:0.002), however, higher treatment dose of phosphate and calcitriol has been detected in NC group (P<0.05).

Conclusion: HR treatment and follow-up is challenging and our results showed higher treatment doses leading NC without any change in serum levels, suggesting given higher doses lead higher phoshaturia probably through the stimulation FGF23. However, higher calcitriol doses could improve bone deformities. Safer and more efficacious therapies are needed.

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