ESPE Abstracts (2016) 86 P-P1-125

Spectrum of the Genetic Defects in Hypophosphatemic Rickets in A Group of Turkish Children

Sezer Acara, Roua A. Al-Rijjalb, Korcan Demira, Walaa E. Kattanb, Gonul Catlic, Huda BinEssab, Ayhan Abacia, Bumin Dundarc, Minjing Zoub, Salih Kavukcua, Brian Meyerb, Ece Bobera & Yufei Shib

aDokuz Eylul University, Izmir, Turkey; bKing Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia; cIzmir Katip Celebi University, Izmir, Turkey

Background: There exists limited data regarding genetic etiology of hypophosphatemic rickets in Turkey.

Objective and hypotheses: To investigate the type of genetic defect in 16 index children and their families (12 unrelated, 1 related).

Method: Following clinical and laboratory assessment, PHEX analysis was made initially unless a mutation in another gene was suspected. If negative, FGF23, SLC34A3, SLC34A1, and CYP27B1 genes were analyzed sequentially.

Results: We identified 21 patients (16 children, five adults) with hypophosphatemic rickets. Sixteen of them (76.2%) had findings related with rickets and 12 (56%) had short stature. Calcium levels were normal, phosphorus low, ALP markedly elevated, and parathormone normal or mildly elevated in all patients. We found 10 different PHEX mutations in 17 patients (80.9%), two novel SLC34A3 mutations in two siblings (9.5%), and no mutation in two patients (9.5%). Five PHEX mutations were de novo. Four novel PHEX mutations were: c.978_982dupCTACC (frameshift), c.1586+2T>G (splice site), c.436+1G>T (splice site), and c.1217G>T (p.C406F). Affected parents were all symptomatic but none were diagnosed previously.

Conclusion: Present study revealed that PHEX mutation seems to be the most prevalent mutation in Turkey as well. More attention should be paid to hypophosphatemia by the clinicians since some cases remain undiagnosed both during childhood and adulthood.