Browsing by Author "Guthrie, Lori C."

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    Autoimmune hyperphosphatemic tumoral calcinosis in a patient with FGF23 autoantibodies
    (American Society for Clinical Investigation, 2018-12-03) Roberts, Mary Scott; Burbelo, Peter D.; Egli-Spichtig, Daniela; Perwad, Farzana; Romero, Christopher J.; Ichikawa, Shoji; Farrow, Emily; Econs, Michael J.; Guthrie, Lori C.; Collins, Michael T.; Gafni, Rachel I.; Medicine, School of Medicine
    Hyperphosphatemic familial tumoral calcinosis (HFTC)/hyperostosis-hyperphosphatemia syndrome (HHS) is an autosomal recessive disorder of ectopic calcification due to deficiency of or resistance to intact fibroblast growth factor 23 (iFGF23). Inactivating mutations in FGF23, N-acetylgalactosaminyltransferase 3 (GALNT3), or KLOTHO (KL) have been reported as causing HFTC/HHS. We present what we believe is the first identified case of autoimmune hyperphosphatemic tumoral calcinosis in an 8-year-old boy. In addition to the classical clinical and biochemical features of hyperphosphatemic tumoral calcinosis, the patient exhibited markedly elevated intact and C-terminal FGF23 levels, suggestive of FGF23 resistance. However, no mutations in FGF23, KL, or FGF receptor 1 (FGFR1) were identified. He subsequently developed type 1 diabetes mellitus, which raised the possibility of an autoimmune cause for hyperphosphatemic tumoral calcinosis. Luciferase immunoprecipitation systems revealed markedly elevated FGF23 autoantibodies without detectable FGFR1 or Klotho autoantibodies. Using an in vitro FGF23 functional assay, we found that the FGF23 autoantibodies in the patient's plasma blocked downstream signaling via the MAPK/ERK signaling pathway in a dose-dependent manner. Thus, this report describes the first case, to our knowledge, of autoimmune hyperphosphatemic tumoral calcinosis with pathogenic autoantibodies targeting FGF23. Identification of this pathophysiology extends the etiologic spectrum of hyperphosphatemic tumoral calcinosis and suggests that immunomodulatory therapy may be an effective treatment.
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    Phenotypic and Genotypic Characterization and Treatment of a Cohort with Familial Tumoral Calcinosis/Hyperostosis-Hyperphosphatemia Syndrome
    (Wiley, 2016-10) Ramnitz, Mary Scott; Gourh, Pravitt; Goldbach-Mansky, Raphaela; Wodajo, Felasfa; Ichikawa, Shoji; Econs, Michael J.; White, Kenneth; Molinolo, Alfredo; Chen, Marcus Y.; Heller, Theo; Del Rivero, Jaydira; Seo-Mayer, Patricia; Arabshahi, Bita; Jackson, Malaka B.; Hatab, Sarah; McCarthy, Edward; Guthrie, Lori C.; Brillante, Beth A.; Gafni, Rachel I.; Collins, Michael T.; Medicine, School of Medicine
    Familial tumoral calcinosis (FTC)/hyperostosis-hyperphosphatemia syndrome (HHS) is a rare disorder caused by mutations in the genes encoding fibroblast growth factor-23 (FGF23), N-acetylgalactosaminyltransferase 3 (GALNT3), or KLOTHO. The result is functional deficiency of, or resistance to, intact FGF23 (iFGF23), causing hyperphosphatemia, increased renal tubular reabsorption of phosphorus (TRP), elevated or inappropriately normal 1,25-dihydroxyvitamin D3 (1,25D), ectopic calcifications and/or diaphyseal hyperostosis. Eight subjects with FTC/HHS were studied and treated. Clinical manifestations varied, even within families, ranging from asymptomatic to large, disabling calcifications. All subjects had hyperphosphatemia, increased TRP, and elevated or inappropriately normal 1,25D. C-terminal FGF23 was markedly elevated while iFGF23 was comparatively low, consistent with increased FGF23 cleavage. Radiographs ranged from diaphyseal hyperostosis to massive calcification. Two subjects with severe calcifications also had overwhelming systemic inflammation and elevated C-reactive protein (CRP). GALNT3 mutations were identified in 7 subjects; no causative mutation was found in the eighth. Biopsies from 4 subjects showed ectopic calcification and chronic inflammation, with areas of heterotopic ossification observed in 1 subject. Treatment with low phosphate diet, phosphate binders, and phosphaturia-inducing therapies was prescribed with variable response. One subject experienced complete resolution of a calcific mass after 13 months of medical treatment. In the 2 subjects with systemic inflammation, interleukin-1 (IL-1) antagonists significantly decreased CRP levels with resolution of calcinosis cutis and peri-lesional inflammation in one subject and improvement of overall well-being in both subjects. This cohort expands the phenotype and genotype of FTC/HHS and demonstrates the range of clinical manifestations despite similar biochemical profiles and genetic mutations. Overwhelming systemic inflammation has not been described previously in FTC/HHS; the response to IL-1 antagonists suggests that anti-inflammatory drugs may be useful adjuvants. In addition, this is the first description of heterotopic ossification reported in FTC/HHS, possibly mediated by the adjacent inflammation.