Juvenile onset systemic lupus erythematosus: a possible role for vitamin D in disease status and bone health

Abstract

In juvenile onset systemic lupus erythematosus (JoSLE), evidence for the association between vitamin D status, lupus activity, and bone health is very limited and not conclusive. The aim of this study was, therefore, to assess in JoSLE patients the possible relevance of vitamin D deficiency in disease and bone parameters. Fifty-seven JoSLE patients were initially compared to 37 age, race and body mass index (BMI) -matched healthy controls. The serum concentration of 25 hydroxyvitamin D (25OHD) was determined by radioimmunoassay. Patients with 25OHD deficiency (≤20 ng/mL) were compared to those with levels >20 ng/mL. Disease activity was evaluated by SLE Disease Activity Index (SLEDAI). Bone mineral density (BMD) and body composition (BC) were measured using dual-energy X-ray absorptiometry (DXA). 25OHD levels were similar in patients and controls (21.44 ± 7.91 vs 22.54 ± 8.25 ng/mL, p = 0.519), regardless of supplementation (65% of patients and none in controls). Thirty-one patients with 25OHD deficiency (≤20 ng/mL) were further compared to the 26 JoSLE patients with levels >20 ng/mL. These two groups were well-balanced regarding vitamin D confounding variables: age (p = 0.100), ethnicity (p = 1.000), BMI (p = 0.911), season (p = 0.502), frequency of vitamin D supplementation (p = 0.587), creatinine (p = 0.751), renal involvement (p = 0.597), fat mass (p = 0.764), lean mass (p = 0.549), previous/current use of glucocorticoids(GC) (p = 1.0), immunosuppressors (p = 0.765), and mean current daily dose of GC (p = 0.345). Patients with vitamin D deficiency had higher SLEDAI (3.35 ± 4.35 vs 1.00 ± 2.48, p = 0.018), lower C4 levels (12.79 ± 6.78 vs 18.38 ± 12.24 mg/dL, p = 0.038), lower spine BMD (0.798 ± 0.148 vs 0.880 ± 0.127 g/cm(2), p = 0.037) and whole body BMD (0.962 ± 0.109 vs 1.027 ± 0.098 g/cm(2), p = 0.024). JoSLE vitamin D deficiency, in spite of conventional vitamin D supplementation, affects bone and disease activity status independent of therapy and fat mass reinforcing the recommendation to achieve adequate levels.