Evaluation of Volumetric Bone Mineral Density, Bone Microarchitecture, and Bone Strength in Patients with Achondroplasia Caused by FGFR3 c.1138G > A Mutation.

Achondroplasia (ACH) is a skeletal disorder caused by fibroblast growth factor receptor 3 (FGFR3) variants. Volumetric bone mineral density (vBMD), bone microarchitecture, and strength have not been evaluated in these patients previously. This study aims to evaluate vBMD, bone microarchitecture, and strength in ACH patients. Seventeen patients underwent clinical and biochemical evaluations, and genetic testing. High-resolution peripheral quantitative computed tomography was performed in 10 ACH patients and 21 age- and sex-matched healthy subjects. All individuals had the hotspot mutation of c.1138G > A in FGFR3. Linear growth retardation, disproportionate short stature, and genu varum are the most common manifestations. The mean height was 108.82 ± 24.08 cm (Z score: - 5.72 ± 0.96). Total vBMD in the ACH and the control groups was 427.08 ± 49.29 mg HA/cm3 versus 300.35 ± 69.92 mg HA/cm3 (p < 0.001) at the radius and 336.90 ± 79.33 mg HA/cm3 versus 292.20 ± 62.35 mg HA/cm3 (p = 0.098) at the tibia; both at the radius and tibia, vBMD of trabecular bones was significantly lower in the ACH group than in the control group, but vBMD of cortical bones was slightly higher in the ACH group. Trabecular separation and cortical thickness in the ACH group were significantly higher than those in the control group, but trabecular number was significantly decreased in the ACH group. Stiffness and failure load were only better at the radius in the ACH group. ACH patients have higher total and cortical vBMD, lower trabecular vBMD, worse trabecular bone microarchitecture, thicker cortical bone thickness, and better estimated bone strength.