Is vitamin D deficiency linked to disease activity in juvenile idiopathic arthritis?

This study investigated if vitamin D levels and disease activity are linked in juvenile idiopathic arthritis (JIA). They found that low vitamin D levels were associated with higher disease activity.

Juvenile idiopathic arthritis (JIA) is caused by inflammation in the joints. The cause of JIA is unknown. In JIA, the body’s immune system attacks healthy joint tissue. This is why JIA is called an auto-immune (AI) disease. To treat JIA, disease-modifying anti-rheumatic drugs (DMARDs) are prescribed. 

Some research suggests vitamin D may be important in a healthy immune system. In other AI diseases such as rheumatoid arthritis, low vitamin D levels are often reported. One study showed vitamin D levels are low in patients with JIA. It is unclear if vitamin D levels are associated with higher disease activity in patients with JIA.

This study included 360 patients with newly-diagnosed JIA. A blood sample was taken at the beginning of the study and 3-36 months later. On average, there were 5-7 months between samples being taken. Disease activity was measured using a standardized scale. Vitamin D deficiency was defined as lower than 20 ng/ml.

44% of patients were deficient in vitamin D at the beginning of the study. Patients with low vitamin D levels had higher disease activity scores. Patients that were not yet treated with DMARDs had significantly lower vitamin D levels. 41% of patients with low vitamin D developed uveitis (inflammation in the eye) compared to 14% of those with sufficient vitamin D.

The authors concluded that low vitamin D levels were associated with higher disease activity in patients with JIA.

It is unknown if vitamin D contributes to JIA. Low vitamin D may be a symptom of JIA and not a cause. Also, this study did not record if vitamin D supplements were used.