Bone marrow fat fraction and R2* in sickle cell disease: Associations with hemolysis, iron metabolism, and disease severity.

BACKGROUND

Six-point DIXON MRI provides fat fraction (FF) and R2* maps, enabling noninvasive assessment of bone marrow (BM) fat and iron-related changes. In sickle cell disease (SCD), chronic hemolysis and compensatory hematopoiesis may alter BM composition. This study aimed to investigate the relationship between BM FF and R2* measurements and laboratory indices of hemolysis and iron metabolism in SCD patients.

METHODS

This cross-sectional study included healthy individuals and SCD patients matched for age, sex, and weight. All participants underwent pelvic and upper abdominal MRI to quantify FF and R2* in the iliac bone (IB) and liver. Associations between FF, R2*, and markers of hemolysis were evaluated. ROC curve analysis assessed the ability of MRI-derived parameters to identify patients with a higher degree of hemolysis (HDH) and elevated ferritin levels.

RESULTS

Thirty-seven healthy individuals and 37 SCD patients were included. Mean IB-FF was 16.9%(±13.8%) in SCD patients and 49.3%(±11.7%) in controls (p < 0.001). Mean IB-R2* was 80.9 s-1(±25.6 s-1) and 69.8 s-1(±14.1 s-1), respectively (p = 0.024). Mean liver R2* was higher in SCD patients (65.0 ± 39.2 s-1 vs. 41.1 ± 15.0 s-1,p = 0.001). Laboratory indices were consistent with increased hemolytic activity in SCD patients. IB-R2* correlated moderately with ferritin in overall SCD group (R = 0.699,p < 0.001), strongly in HbSS subtype (R = 0.816,p < 0.001). Liver R2* and IB-FF demonstrated high accuracy for detecting elevated ferritin levels and HDH, respectively.

CONCLUSIONS

MRI-derived IB-FF and IB-R2* were associated with laboratory indices of hemolysis and disease severity in SCD, findings that may reflect bone marrow compositional changes related to chronic hemolytic stress and erythropoietic adaptation.