Chief Editor’s Note: This article is the 11th of 18 that will be published in 2008 for which a total of up to 18 AMA PRA Category 1 Credits™ can be earned. Instructions for how credits can be earned precede the CME Examination at the back of this issue.
An Unusual Etiology
Whitney W. Brown, MD,* Kenneth L. McCormick, MD,† Kenneth E. White, PhD,‡Holly J. Garringer, PhD,§ and Emily G. Farrow, MS¶
Abstract: Tumoral calcinosis (TC) is a disorder of enhanced renal tubular phosphate reabsorption resulting in hyperphosphatemia and ectopic calciﬁcations. Gene analyses have conﬁrmed that destabilizing mutations within ﬁbroblast growth factor-23 (FGF23) and GalNAc transferase-3 (GALNT3) are responsible for heritable TC. Herein, we present apatient with phenotypic and biochemical features of TC, whose evaluation revealed no mutations in either the FGF23 or GALNT3 genes and normal circulating C-terminal and intact FGF23 concentrations. The patient is a 12-year-old African American man with ectopic, subcutaneous mineral deposits, with a diagnosis of tumoral calcinosis based on collective clinical features. Plasma FGF23 concentrations weredetermined using both an assay that measures full-length FGF23 and one that recognizes the C-terminal portion. Gene analysis was performed on DNA isolated from peripheral WBCs. The patient’s calcium and PTH concentrations were normal. Serum phosphorus concentrations ranged 5 to 6.7 mg/dL. 1,25-Hydroxy vitamin D levels were elevated. FGF23 C-terminal fragment concentrations were 53.79 RU/mL(reference interval 55 50 RU/mL) and intact FGF23 concentrations were 11 pg/mL (reference interval 28 2.2 pg/mL). Gene analysis showed no mutations in either FGF23 or GALNT3 genes.
*Fellow, Pediatric Endocrinology, and †Director and Professor of Pediatric Endocrinology, University of Alabama School of Medicine, Birmingham, Alabama; ‡Assistant Professor of Medical and Molecular Genetics, §PostdoctoralFellow, and ¶Graduate Student, Indiana University School of Medicine, Indianapolis, Indiana. Dr. White has disclosed that he is/was the recipient of grant/research support from Kirin Pharmaceutical. Dr. White has also disclosed that he receives, and in the previous 12 months has received, royalties for licensing FGF23 to Kirin Pharmaceutical. The remaining authors have disclosed that they have nosigniﬁcant relationships with or ﬁnancial interests in any commercial organizations pertaining to this educational activity. All staff in a position to control the content of this CME activity have disclosed that they have no ﬁnancial relationships with, or ﬁnancial interests in, any commercial companies pertaining to this educational activity. Lippincott CME Institute has identiﬁed and resolved allfaculty and staff conﬂicts of interest regarding this educational activity. Reprints: Whitney W. Brown, MD, University of Alabama School of Medicine, Department of Pediatric Endocrinology, 1601 4th Avenue South, Suite 230, Birmingham, AL 35233. E-mail: firstname.lastname@example.org. Copyright © 2008 by Lippincott Williams & Wilkins ISSN: 1051-2144/08/1804-0191 DOI: 10.1097/TEN.0b013e31817ffef7
Reportedcases of TC due to FGF23 and GALNT3 mutations have similar clinical and laboratory features. Our patient has most of the “classic” TC phenotypic features, but has normal circulating levels of C-terminal and intact FGF23, and no detected mutations of either the FGF23 or GALNT3 genes. Therefore, our case likely represents a new, yet undetermined, cause of TC. Key Words: tumoral calcinosis, ﬁbroblastgrowth factor 23, GALNT3 (The Endocrinologist 2008;18: 191–194)
Learning Objectives • Describe the clinical characteristics of the subcutaneous
mineral deposits found in this patient with tumoral calcinosis (TC). • Point out genetic differences between this patient and those documented as having heritable TC. • Summarize the ways in which lesions of TC respond to dietary measures, drug...