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Case Reports in Pediatrics
Volume 2013 (2013), Article ID 354314, 5 pages
http://dx.doi.org/10.1155/2013/354314
Case Report

Successful Medical Therapy for Hypophosphatemic Rickets due to Mitochondrial Complex I Deficiency Induced de Toni-Debré-Fanconi Syndrome

1Division of Endocrinology, Nationwide Children’s Hospital, The Ohio State University College of Medicine, 700 Children’s Drive, Columbus, OH 43205, USA
2Division of Nephrology, Nationwide Children’s Hospital, The Ohio State University College of Medicine, Columbus, OH 43205, USA
3Division of Orthopedics, Nationwide Children’s Hospital, The Ohio State University College of Medicine, Columbus, OH 43205, USA
4Center for Cardiovascular and Pulmonary Research, Department of Pediatrics, Nationwide Children’s Hospital, The Ohio State University College of Medicine, Columbus, OH 43205, USA

Received 19 September 2013; Accepted 14 November 2013

Academic Editors: E. Barbi and P. Spennato

Copyright © 2013 Sasigarn A. Bowden et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Primary de Toni-Debré-Fanconi syndrome is a non-FGF23-mediated hypophosphatemic disorder due to a primary defect in renal proximal tubule cell function resulting in hyperphosphaturia, renal tubular acidosis, glycosuria, and generalized aminoaciduria. The orthopaedic sequela and response to treatment of this rare disorder are limited in the literature. Herein we report a long term followup of a 10-year-old female presenting at 1 year of age with rickets initially misdiagnosed as vitamin D deficiency rickets. She was referred to the metabolic bone and genetics clinics at 5 years of age with severe genu valgum deformities of 24 degrees and worsening rickets. She had polyuria, polydipsia, enuresis, and bone pain. Diagnosis of hypophosphatemic rickets due to de Toni-Debré-Fanconi syndrome was subsequently made. Respiratory chain enzyme analysis identified a complex I mitochondrial deficiency as the underlying cause. She was treated with phosphate (50–70 mg/kg/day), calcitriol (30 ng/kg/day), and sodium citrate with resolution of bone pain and normal growth. By 10 years of age, her genu valgus deformities were 4 degrees with healing of rickets. Her excellent orthopaedic outcome despite late proper medical therapy is likely due to the intrinsic renal tubular defect that is more responsive to combined alkali, phosphate, and calcitriol therapy.