Content area
Full Text
The epidemic scourge of rickets in the 19th century was caused by vitamin D deficiency due to inadequate sun exposure and resulted in growth retardation, muscle weakness, skeletal deformities, hypocalcemia, tetany, and seizures. The encouragement of sensible sun exposure and the fortification of milk with vitamin D resulted in almost complete eradication of the disease. Vitamin D (where D represents D2 or Da) is biologically inert and metabolized in the liver to 25-hydroxyvitamin D [25(OH)D], the major circulating form of vitamin D that is used to determine vitamin D status. 25(OH)D is activated in the kidneys to 1,25-dihydroxyvitamin D [1,25(OH)2D], which regulates calcium, phosphorus, and bone metabolism. Vitamin D deficiency has again become an epidemic in children, and rickets has become a global health issue. In addition to vitamin D deficiency, calcium deficiency and acquired and inherited disorders of vitamin D, calcium, and phosphorus metabolism cause rickets. This review summarizes the role of vitamin D in the prevention of rickets and its importance in the overall health and welfare of infants and children.
Nonstandard abbreviations used: 1-OHase, 25-hydroxyvitamin D-1α-hydroxylase; 1,25(OH)2D, 1,25-dihydroxyvitamin D; 25(OH)D, 25-hydroxyvitamin D; DBP, vitamin D-binding protein; FGF23, fibroblast growth factor 23; PHEX, phosphate-regulating endopeptidase homolog, X-linked; PTH, parathyroid hormone; RANKL, receptor activator of NF-κB ligand; RXR, retinoic acid X receptor, SPF, sun protection factor, UVB, ultraviolet B; VDR, vitamin D receptor; VDRE, vitamin D-responsive element.
Historical perspective
In the mid-1600s, most children who lived in the crowded and polluted industrialized cities of northern Europe developed a severe bone-deforming disease that was characterized by growth retardation, enlargement of the epiphyses of the long bones, deformities of the legs, bending of the spine, knobby projections of the ribcage, and weak and toneless muscles (1,2) (Figure 1). In the latter part of the 19th century, autopsy studies done in Boston and Leiden, The Netherlands, showed that 80-90% of children had rickets.
In 1822, Sniadecki (3) recognized the importance of sun exposure for the prevention and cure of rickets. Palm (4) extended these observations in 1890 and promoted systemic use of sun baths to prevent rickets. In 1919, Huldschinski (5, 6) found that exposing children to radiation from a sun quartz lamp (mercury arc lamp) or carbon are lamp for one hour 3 times a...