High bone mineral density in sickle cell disease: Prevalence and characteristics

Background Osteosclerosis (OSC) is a rarely studied complication of sickle cell disease (SCD). The objective of our study was to determine the prevalence and characteristics of high bone mineral density (BMD) and its radiological features in adult SCD patients. Methods This prospective observational study was conducted from May 2007 to May 2016 in consecutive patients with steady-state SCD at two university hospitals. The BMD of the lumbar spine (L1-L4) and right femoral neck was determined by dual energy X-ray absorptiometry. Clinical, laboratory and radiographic data were recorded. High BMD was defined as a BMD Z-score of at least +2.5 standard deviations at the lumbar spine or hip. The characteristics of the patients with high BMD were compared to those of individuals with low or middle BMD, using multivariate ordinal logistic regression. Results 135 patients (86 women and 49 men) with a median age of 27 (IQR 23-33) years were included. High BMD was diagnosed in 20 (15%) patients with a median age of 33.5 (IQR 28-45) years. The SCD genotypes of these patients were SS in 11, SC in 5, S/beta+ in 3, and S/beta0 in 1. High BMD patients more frequently harbored the S/beta SCD genotype (21% vs 5% in non-high BMD patients; p = 0.047) and were older (p = 0.0007). Compared to patients with low or middle BMD, after adjustment for age and SCD genotype, high BMD patients had a higher prevalence of avascular necrosis history (p = 0.009), higher BMI (p = 0.007), and lower serum resorption marker CTX (p = 0.04), bilirubin (p = 0.02) and parathyroid hormone levels (p = 0.02). There were no differences between groups regarding fracture history, H-shaped vertebrae or other biological variables. Conclusion High-BMD values is a common manifestation in SCD patients, especially in those with the S/beta-thalassemia genotypes. The prevalence of high-BMD in SCD is associated with older age, suggesting that it will be more common in the future because the life span of patients with SCD is increasing thanks to significant progress in SCD treatment.