Bone Mineral Density is Related to CD4⁺ T Cell Counts and Muscle Mass is Associated with B Cells in Common Variable Immunodeficiency Patients

Background: Common variable immunodeficiency (CVID) is a primary immunodeficiency characterized by chronic/recurrent respiratory infections, bronchiectasis, autoimmunity, inflammatory, gastrointestinal diseases and malignancies associated with a chronic inflammatory state and increased risk of osteoporosis and muscle loss. Aim: The aim of this study was to evaluate bone mineral density (BMD), body composition and their relationship with lymphocyte subpopulations in CVID patients. Methods: Dual-energy X-ray absorptiometry was performed to assess BMD, lean mass, and fat mass in CVID patients. Peripheral blood CD4⁺, CD8⁺, and CD19⁺ cells were measured using flow cytometry. Results: Thirty-three patients (37.3 ± 10.8 years old) were examined. Although only 11.8% of the individuals were malnourished (BMI <18.5 kg/m2), 27.7% of them had low skeletal muscle mass index (SMI), and 57.6% of them had low BMD. Patients with osteopenia/osteoporosis presented lower weight (p = 0.007), lean mass (p = 0.011), appendicular lean mass (p = 0.011), SMI (p = 0.017), and CD4+ count (p = 0.030). Regression models showed a positive association between CD4+ count and bone/muscle parameters, whereas CD19+ B cell count was only associated with muscle variables. Analysis of ROC curves indicated a cutoff value of CD4+ count (657 cells/mm3; AUC: 0.71, 95% CI 0.52-0.90) which was related to low BMD. Weight (p = 0.004), lean mass (p = 0.027), appendicular lean mass (p = 0.022), SMI (p = 0.029), total bone mineral content (p = 0.005), lumbar (p = 0.005), femoral neck (p = 0.035), and total hip BMD (p<0.001) were found to be lower in patients with CD4+ count below the cutoff. Conclusion: CVID patients presented with low BMD, which was associated with CD4+ count. Moreover, low muscle parameters were correlated with B cell count.