ESPE Abstracts (2015) 84 P-2-217

The Spectrum of Molecular Defects in 64 Patients with Hypophosphatemic Rickets Identified by Targeted Next-Generation Sequencing

Kristina Kulikovaa, Anna Kolodkinaa, Evgeny Vasilyeva, Vasily Petrova, Fedor Gofmanb, Anatoly Horkinb, Vladimir Kenisc, Michael Petrovd & Anatoly Tiulpakova

aEndocrinology Research Centre, Moscow, Russia; bFSI RISC RTO of Federal agency of High Medical Technology, Kurgan, Russia; cTurner Scientific and Research Institute for Childrens Orthopedics, Saint-Petersburg, Russia; dV.Morozov Childrens Hospital, Moscow, Russia

Background: Hypophosphatemic rickets (HR) comprises a group of inherited forms of rickets characterised by renal phosphate wasting. To date more than 10 genes are associated with HR, and a comprehensive molecular diagnosis in these disorders is technically difficult to perform.

Objective and hypotheses: To assess the value of targeted next-generation sequencing (NGS) used for molecular analysis of candidate genes of HR.

Method: 64 patients (aged, of 3 months to 45 years; females, n=32; males, n=32) with clinical and radiological findings of rickets, low serum phosphate and low tubular reabsorption of phosphate were included. There were 29 familial and 35 sporadic cases from 58 families. ‘Rickets panel’ genes were sequenced using a custom Ion Ampliseq gene panel and PGM semiconductor sequencer (Ion Torrent). Bioinformatic analysis was performed using Torrent Suite (Ion Torrent) and ANNOVAR ( software packages.

Results: Mutations were identified in 100% of familial and 88,5% of sporadic cases. In 60 probands mutations were detected in PHEX, 38 of which were novel. Out of the 54 PHEX mutations there were deletions (n=7), missense (n=13), nonsense (n=11), insertion and deletions (n=16) and splice site mutations (n=7). One subject had both DMP1 and PHEX mutations. No mutations were detected in FGF23, SLC34A1, SLC34A3, SLC9A3R1, ENPP1, CLCN5 and SLC2A2 genes.

Conclusion: The study confirmed predominance of PHEX mutations among the patients with HR. Nevertheless, the large size and complexity of PHEX gene makes the targeted NGS a feasible tool for diagnostics of HR.

Funding: This work was supported by Alfa-Endo Program of Charities Aid Foundation (CAF) Russia.