25(OH)Vitamin D Deficiency and Calcifediol Treatment in Pediatrics

Abstract

Vitamin D is essential for the normal mineralization of bones during childhood. Although diet and adequate sun exposure should provide enough of this nutrient, there is a high prevalence of vitamin D deficiency rickets worldwide. Children with certain conditions that lead to decreased vitamin D production and/or absorption are at the greatest risk of nutritional rickets. In addition, several rare genetic alterations are also associated with severe forms of vitamin-D-resistant or -dependent rickets. Although vitamin D3 is the threshold nutrient for the vitamin D endocrine system (VDES), direct measurement of circulating vitamin D3 itself is not a good marker of the nutritional status of the system. Calcifediol (or 25(OH)D) serum levels are used to assess VDES status. While there is no clear consensus among the different scientific associations on calcifediol status, many clinical trials have demonstrated the benefit of ensuring normal 25(OH)D serum levels and calcium intake for the prevention or treatment of nutritional rickets in childhood. Therefore, during the first year of life, infants should receive vitamin D treatment with at least 400 IU/day. In addition, a diet should ensure a normal calcium intake. Healthy lifestyle habits to prevent vitamin D deficiency should be encouraged during childhood. In children who develop clinical signs of rickets, adequate treatment with vitamin D and calcium should be guaranteed. Children with additional risk factors for 25(OH)D deficiency and nutritional rickets should be assessed periodically and treated promptly to prevent further bone damage.

Keywords: calcifediol; genetic forms of rickets; nutritional rickets; vitamin D deficiency; vitamin D treatment.

Figure 1

Schematic representation of VDES metabolism and the main genes involved. The CYP2R1, CYP27B1, CYP24A1, and CYP3A4 genes encode the enzymes vitamin D 25-hydroxylase, 25-hydroxyvitamin D3-1-alpha-hydroxylase, vitamin D 24-hydroxylase and cytochrome P450 3A4, respectively. The VDR gene encodes the vitamin D receptor. The DHCR7 gene encodes delta-7-dehydrocholesterol reductase. The HNRNPC gene encodes Heterogeneous Nuclear Ribonucleoprotein C. VDDR1A, vitamin D-dependent rickets type 1A; VDDR1B, vitamin D hydroxylation-deficient rickets type 1B; VDDR2A, vitamin D-dependent rickets type 2A; VDDR2B, vitamin D-dependent rickets type 2B with normal vitamin D receptor; VDDR3, dominant vitamin D-dependent rickets type 3.

Figure 2

Diagnostic algorithm of the different forms of rickets.