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What causes rickets?
Regardless of the type of rickets, the cause is always either due to a deficiency of vitamin D, calcium, or phosphate. Three common causes of rickets include nutritional rickets, hypophosphatemic rickets, and renal rickets.
Nutritional rickets, also called osteomalacia, is a condition caused by vitamin D deficiency. Vitamin D is a fat-soluble vitamin that is essential for the normal formation of bones and teeth and necessary for the appropriate absorption of calcium and phosphorus from the bowels. It occurs naturally in very small quantities in some foods such as saltwater fish (salmon, sardines, herring, and fish-liver oils). Vitamin D is also naturally synthesized by skin cells in response to sunlight exposure. It is necessary for the appropriate absorption of calcium from the gut.
Infants and children most at risk for developing nutritional rickets include dark-skinned infants, exclusively breastfed infants, and infants who are born to mothers who are vitamin D deficient. In addition, older children who are kept out of direct sunlight or who have vegan diets may also be at risk.
Hypophosphatemic rickets is caused by chronically low levels of phosphate in the blood. The bones become painfully soft and pliable. This is caused by a genetic dominant X-linked defect in the ability for the kidneys to control the amount of phosphate excreted in the urine. The individual affected is able to absorb phosphate and calcium, but the phosphate is lost through the kidneys into the urine. This is not caused by a vitamin D deficiency. Patients with hypophosphatemic rickets typically have obvious symptoms by 1 year of age. Treatment is generally through nutritional supplements of phosphate and calcitriol (the activated form of vitamin D).
Renal (kidney) rickets
Similar to hypophosphatemic rickets, renal rickets is caused by a number of kidney disorders. Individuals suffering from kidney disease often have decreased ability to regulate the amounts of electrolytes lost in the urine. This includes calcium and phosphate, and therefore the affected individuals develop symptoms almost identical to severe nutritional rickets. Treatment of the underlying kidney problem and nutritional supplementation are recommended for these patients.