Abstract
Raine syndrome is characterized by FGF23-mediated hypophosphatemic osteomalacia with osteosclerosis caused by mutations in the FAM20C gene. We report a case of a 72-year-old man who presented with rapid progressive spontaneous osteonecrosis of the knee (SONK). A full osteologic assessment including dual energy X-ray absorptiometry (DXA), high-resolution peripheral quantitative computed tomography (HR-pQCT), and serum analyses revealed a high bone mass in the lumbar spine and hip (DXA T-score + 7.5 and + 4.7/+4.2) with increased bone microstructural parameters in the distal radius and tibia (BV/TV 127%, 140% of the age-matched mean, respectively), as well as a low bone turnover state. Phosphate levels were low due to renal phosphate wasting and high FGF23 levels (126.5 pg/ml, reference range 23.2–95.4 pg/ml). Using gene panel sequencing, we identified a novel FAM20C heterozygous missense mutation in combination with a homozygous duplication that potentially alters splicing. Taken together, this is the first case of mild Raine syndrome with spontaneous osteonecrosis of the knee, phosphate wasting, and a pronounced trabecular high bone mass phenotype.
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Funding
This project has received funding from the German Federal Ministry of Education and Research (BMBF) within the project “Detection and Individualized Management of Early Onset Osteoporosis (DIMEOS).”
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Rolvien, T., Kornak, U., Schinke, T. et al. A novel FAM20C mutation causing hypophosphatemic osteomalacia with osteosclerosis (mild Raine syndrome) in an elderly man with spontaneous osteonecrosis of the knee. Osteoporos Int 30, 685–689 (2019). https://doi.org/10.1007/s00198-018-4667-6
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DOI: https://doi.org/10.1007/s00198-018-4667-6