Hypovitaminosis D is Associated with Greater Body Mass Index and Disease Activity in Pediatric Systemic Lupus Erythematosus

Objectives

To determine whether pediatric systemic lupus erythematosus (SLE) is associated with alterations in the vitamin D-parathyroid hormone (PTH) axis and to assess the relation between vitamin D deficiency and SLE activity.

Study Design

25-hydroxy vitamin D [25(OH)D], 1,25-dihydroxy vitamin D [1,25(OH)₂D], and intact PTH were measured in subjects with SLE (n = 38) and healthy controls (n = 207), ages 5 to 21 years. Vitamin D status and its relation with disease activity were assessed using multivariable logistic and linear regression.

Results

Severe vitamin D deficiency (25(OH)D <10 ng/ml) was observed in a significantly higher proportion of subjects with SLE (36.8% vs 9.2%, P < .001). In SLE, the odds ratio (OR) for severe deficiency was 2.37 (P = .09), adjusting for age, sex, race, and season. However, for each 1 SD greater body mass index (BMI) z-score, 25(OH)D levels were 4.2 ng/mL lower (P = .01) in SLE, compared with controls. Adjusting for 25(OH)D levels, SLE was associated with significantly lower 1,25(OH)₂D (P < .001) and intact PTH levels (P = .03). Greater SLE disease activity index scores were observed in those with 25(OH)D <20 ng/mL (P = .01).

Conclusions

SLE was associated with vitamin D deficiency, particularly among those subjects with SLE who were overweight. Future studies should assess the effect of vitamin D supplementation on skeletal and nonskeletal outcomes in SLE.

BMI, Body mass index, CASR, Calcium-sensing receptor, PTH, Parathyroid hormone, SLE, Systemic lupus erythematosus, SLEDAI, SLE disease activity index, (1,25[OH]₂D), 1,25-dihydroxy vitamin D, (25[OH]D), 25-hydroxy vitamin D