Microarchitectural parameters and bone mineral density in patients with Tumor-Induced Osteomalacia by HR-pQCT and DXA.

Tumor-induced Osteomalacia (TIO) is a rare paraneoplastic condition characterized by decreased tubular phosphate reabsorption. The purpose of this study is to evaluate bone mineral density (BMD) and microarchitecture in six TIO patients compared to eighteen healthy controls.Volumetric BMD and microarchitecture were evaluated by high-resolution peripheral quantitative computed tomography (HR-pQCT), and areal BMD by dual energy X-ray absorptiometry (DXA). Differences between groups were significant for p-value <0.05.All TIO subjects were healthy until development of diffuse bone pain and multiple skeletal fractures and deformities. At baseline, sPi and TmPi/GFR were low and patients were on vitamin D and phosphate replacement at the study. Compared to controls, TIO patients had lower aBMD at lumbar spine and hip, and lower vBMD at trabecular, cortical and entire bone, at distal radius (R) and distal tibia (T): Dtrab (R=118.3 x 177.1; T=72.3 x 161.3 gHA/cm3 ); Dcomp (R=782.3 x 866.5; T=789.1 x 900.9 gHA/cm3 ); Dtotal (R=234.5 x 317; T=167.1 x 295.8 gHA/cm3 ). Bone microarchitecture was very heterogeneous among patients, and significantly different from controls: lower Ct.Th (R=0.59 x 0.80; T=0.90 x 1.31 mm), BV/TV (R=0.09 x 0.14; T=0.06 x 0.13) and Tb.N (R=1.46 x 2.10; T=0.93 x 1.96 mm-1 ) and also higher Tb.Sp (R=0.70 x 0.41; T=1.28 x 0.45mm) and Tb.1/N.SD (R=0.42 x 0.18; T=0.87 x 0.20mm).In this original study of TIO patients, DXA and HR-pQCT evaluation identified lower areal and volumetric BMD and severely impaired microarchitecture at cortical and trabecular bones, which probably contribute to bone fragility and fractures.

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Authors: Danielle Alves Brandão Mendes, Maria Caroline Alves Coelho, Bárbara Gehrke, Leandro Kasuki Jomori de Pinho, Luis Felipe Cardoso Lima, Francisco de Paula Paranhos Neto, Laura Maria Carvalho de Mendonça, Maria Lucia Fleiuss Farias, Miguel Madeira