Clinical, hormonal, biochemical and genetic characteristics of 75 patients with hypophosphatemic rickets

Aim — the present research was aimed at identifying the genetic causes for hr in patients, as well as evaluating the clinical, hormonal and biochemical characteristics of the disease in this group of patients.

Material and methods. 75 patients (aged, of 3 months to 57 years; females, n=38; males, n=37) with clinical and radiological findings of rickets, low serum phosphate and low tubular reabsorption of phosphate were included. ‘rickets panel’ genes were sequenced using a custom Ion Ampliseq gene panel and PGM semiconductor sequencer (Ion Torrent). The panel included primers for multiplex amplification of 22 genes associated with genetic calcium metabolism dysfunctions. Bioinformatic analysis was performed using torrent suite (Ion Torrent) and ANNOVAR software packages.

Results. Out of the 75 patients 36 were diagnosed with familial form of hr, and 39 probands had sporadic cases. Out clinical characteristics the most widespread symptoms of the disease included: lower limbs malformations since the patients started to walk (94.5%), hypotonia in the first 12 months of life (70.2%), multiple caries (58%). Mutations were identified in 100% of familial and 88,5% of sporadic cases. In 68 probands (90,5%) mutations were detected in PHEX, 40 of which were novel. For familial forms of the disease mutations were discovered in 100% cases, for sporadic — in 82% cases. One subject had both DMP1 and PHEX mutations. No mutations were detected in FGF23, SLC34A1, SLC34A3, SLC9A3R1, ENPP1, CLClCN5 and SLC2A2 genes.

Conclusion. The study confirmed predominance of PHEX mutations among the patients with HR. The identification of causative agent is very important for antenatal diagnostics for familial forms of disease and enables well-timed conservative treatment.

1. Amatschek S, Haller M, Oberbauer R. Renal phosphate handling in human — what can we learn from hereditary hypophosphataemias? Eur J Clin Invest. 2010;40(6):552-560. doi: 10.1111/J.1365-2362.2010.02286.X.

2. Carpenter TO. The expanding family of hypophosphatemic syndromes. J Bone Miner Metab. 2011;30(1):1-9. doi: 10.1007/S00774-011-0340-2.

3. Francis F, Hennig S, Korn B, et al. A gene (PHEX) with homologies to endopeptidases is mutated in patients with X–linked hypophosphatemic rickets. Nat Genet. 1995;11(2):130-136. doi: 10.1038/Ng1095-130.

4. Chong WH, Molinolo AA, Chen CC, Collins MT. Tumor-induced osteomalacia. Endocrine Related Cancer. 2011;18(3):R53-R77. doi: 10.1530/Erc-11-0006.

5. Adzhubei IA, Schmidt S, Peshkin L, et al. A method and server for predicting damaging missense mutations. Nat Methods. 2010;7(4):248-249. doi: 10.1038/Nmeth0410-248.

6. Beck-Nielsen SS, Brock-Jacobsen B, Gram J, et al. Incidence and prevalence of nutritional and hereditary rickets in Southern Denmark. Eur J Endocrinol. 2008;160(3):491-497. doi: 10.1530/Eje-08-0818.

7. Carpenter TO. New perspectives on the biology and treatment of X-Linked hypophosphatemic rickets. Pediatr Clin North Am. 1997;44(2):443-466. doi: 10.1016/S0031-3955(05)70485-5.

8. White KE, Evans WE, O’riordan JLH, et al. Autosomal dominant hypophosphataemic rickets is associated with mutations in FGF23. Nat Genet. 2000;26(3):345-348. doi: 10.1038/81664.

9. Feng JQ, Ward LM, Liu S, et al. Loss of DMP1 causes rickets and osteomalacia and identifies a role for osteocytes in mineral metabolism. Nat Genet. 2006;38(11):1310-1315. doi: 10.1038/Ng1905.

10. Levy-Litan V, Hershkovitz E, Avizov L, et al. Autosomal-recessive hypophosphatemic rickets is associated with an inactivation mutation in the ENPP1 Gene. Am J Hum Genet. 2010;86(2):273-278. doi: 10.1016/J.Ajhg.2010.01.010.

11. Lorenz-Depiereux B, Schnabel D, Tiosano D, et al. Loss-of-function ENPP1 mutations cause both generalized arterial calcification of infancy and autosomal-recessive hypophosphatemic rickets. Am J Hum Genet. 2010;86(2):267-272. doi: 10.1016/J.Ajhg.2010.01.006.

12. Bergwitz C, Roslin NM, Tieder M, et al. SLC34A3 mutations in patients with hereditary hypophosphatemic rickets with hypercalciuria predict a key role for tht sodium-phosphate cotransporter NaPi-IIc in maintaining phosphate homeostasis. Am J Hum Genet. 2006;78(2):179-192. doi: 10.1086/499409.

13. Cho HY, Lee BH, Choi HJ, et al. Renal manifestations of dent disease and lowe syndrome. Pediatr Nephrol. 2007;23(2):243-249. doi: 10.1007/S00467-007-0686-9.

14. Raeder H, Rafaelsen S, Bjerknes R. Monogenic phosphate balance disorders. 2011. doi: 10.5772/17841.

15. Sabbagh Y, Jones AO, Tenenhouse HS. PHEXdb, a locus-specific database for mutations causing X-linked hypophosphatemia. Hum Mutat. 2000;16(1):1-6. doi: 10.1002/1098-1004(200007)16:1<1::Aid-Humu1>3.0.Co;2-J.

16. Tyynismaa H, Kaitila I, Nanto-Salonen K, et al. Identification of fifteen novel PHEX gene mutations in finnish patients with hypophosphatemic rickets. Hum Mutat. 2000;15(4):383-384. doi: 10.1002/(Sici)1098-1004(200004)15:4<383::Aid-Humu18> 3.0.Co;2-#.

17. Holm IA, Nelson AE, Robinson BG, et al. Mutational analysis and genotype-phenotype correlation pf the PHEX gene in X-linked hypophosphatemic rickets. J Clin Endocr Metab. 2001;86(8):3889-3899. doi: 10.1210/Jcem.86.8.7761.

18. Clausmeyer S, Hesse V, Clemens PC, et al. Mutational analysis of the PHEX gene: novel point mutations and detection of large deletions by MLPA in patients with X-linked hypophosphatemic rickets. Calcif Tissue Int. 2009;85(3):211-220. doi: 10.1007/S00223-009-9260-8.

19. Ruppe MD, Brosnan PG, Au KS, et al. Mutational analysis of PHEX, FGF23 and DMP1 in a cohort of patients with hypophosphatemic rickets. Clin Endocrinol (Oxf). 2011;74(3):312-318. doi: 10.1111/J.1365-2265.2010.03919.X.

20. Beck-Nielsen SS, Brixen K, Gram J, Brusgaard K. Mutational analysis of PHEX, FGF23, DMP1, SLC34A3 and CLCN5 in patients with hypophosphatemic rickets. J Hum Genet. 2012;57(7):453-458. doi: 10.1038/Jhg.2012.56.

21. Gaucher C, Walrant-Debray O, Nguyen T-M, et al. PHEX analysis in 118 pedigrees reveals new genetic clues in hypophosphatemic rickets. Hum Genet. 2009;125(4):401-411. doi: 10.1007/S00439-009-0631-Z.

22. Kinoshita Y, Saito T, Shimizu Y, et al. Mutational analysis of patients with FGF23 related hypophosphatemic rickets. Eur J Endocrinol. 2012. doi: 10.1530/Eje-12-0071.

23. Sabbagh Y, Boileau G, Campos M, et al. Structure and function of disease-causing missense mutations in thephexgene. J Clin Endocr Metab. 2003;88(5):2213-2222. doi: 10.1210/Jc.2002-021809.

24. Levine BS, Kleeman CR, Felsenfeld AJ. The journey from vitamin D-resistant rickets to the regulation of renal phosphate transport. Clin J Am Soc Nephrol. 2009;4(11):1866-1877. doi: 10.2215/Cjn.03000509.

25. Strom TM, Francis F, Lorenz B, et al. PHEX gene deletions in Gy and Hyp mice provide mouse models for X-linked hypophosphatemia. Hum Mol Genet. 1997;6(2):165-171. doi: 10.1093/Hmg/6.2.165.

26. Quarles LD. FGF23, PHEX, and mepe regulation of phosphate homeostasis and skeletal mineralization. Am J Physiol Endocrinol Metab. 2003;285(1):E1-E9. doi: 10.1152/Ajpendo.00016.2003.

27. Rowe PSN. The wrickkened pathways of FGFf23, MEPE and PHEX. Crit Rev Oral Biol Medicine. 2004;15(5):264-281. doi: 10.1177/154411130401500503.

28. Young L, Jernigan RL, Covell DG. A role for surface hydrophobicity in protein-protein recognition. Protein Sci. 2008;3(5):717-729. doi: 10.1002/Pro.5560030501.

29. Ichikawa S, Traxler EA, Estwick SA, et al. Mutational survey of thr PHEX gene in patients with X-Linked hypophosphatemic rickets. Bone. 2008;43(4):663-666. doi: 10.1016/J.Bone.2008.06.002.

30. Pekkarinen T, Lorenz-Depiereux B, Lohman M, Mäkitie O. Unusually severe hypophosphatemic rickets caused by a novel and complex re-arrangement of thephexgene. Am J Med Genet A. 2014;164(11):2931-2937. doi: 10.1002/Ajmg.A.36721.

31. Turan S, Aydin C, Bereket A, et al. Identification of a novel dentin matrix protein-(DMP1) mutation and dental anomalies in a kindred with autosomal recessive hypophosphatemia. Bone. 2010;46(2):402-409. doi: 10.1016/J.Bone.2009.09.016.

32. Pavone V, Testa G, Gioitta Iachino S, et al. Hypophosphatemic Rickets: Etiology, Clinical Features And Treatment. Eur J Orthop Surg Traumatol. 2014;25(2):221-226. doi: 10.1007/S00590-014-1496-Y.

33. Zhang X, Peyret T, Gosselin Nh, et al. Population pharmacokinetic and pharmacodynamic analyses from a 4-month intradose escalation and its subsequent 12-month dose titration studies for a human monoclonal anti-FGF23 Antibody (KRN23) in adults with X-linked hypophosphatemia. The Journal Of Clinical Pharmacology. 2015:n/a-n/a. doi: 10.1002/Jcph.611.

34. Al K, Farr S, Ganger R, et al. Windswept lower limb deformities in patients with hypophosphataemic rickets. Swiss Med Wkly. 2013. doi: 10.4414/Smw.2013.13904.