Conversely, when low levels of vitamin D (deficiency + insufficiency) were compared, together, with respect to sufficient serum levels of the vitamin, the ApaI TG genotype resulted to be significantly higher in the JIA group with normal value of 25(OH) vitamin D. The ApaI TG genotype was also found to be significantly more represented in JIA patients with PTH serum levels less than 15 pg/ml, with respect to patients showing normal PTH values. The gene discussed is PTH; the disease is juvenile idiopathic arthritis.