Rickets is a bone disease most commonly caused worldwide by a deficiency of vitamin D. The deficiency may be caused by a lack of vitamin D in the diet, a lack of exposure to sunlight, or a problem the body has with absorbing or using vitamin D. If left untreated, rickets results in bone deformities.
Vitamin D is a nutrient essential for proper bone formation. It helps regulate the amount of calcium and phosphorus in the blood, and these minerals are important components of bone formation. Vitamin D is called the “sunshine vitamin” because it is formed naturally in the skin in the presence of the ultraviolet * (UV) rays found in sunlight. Vitamin D can also be obtained from food. Vitamin D is added to milk and infant formula * , and egg yolks, liver, cod-liver oil, and other fish oils are good dietary sources of vitamin D.
Rickets is characterized by improper hardening of the bones, resulting in skeletal deformities if left untreated. Rickets affects primarily infants and children because bone growth occurs during childhood. Rickets can occur for a number of reasons.
Rickets can occur because of a nutritional deficiency in vitamin D. In modern times this type of rickets is rare in developed countries. Children growing up in poor communities where vitamin D–rich foods may be scarce are the most susceptible to rickets. Children living in areas where there is a lack of sunshine, such as in the Northern Hemisphere in the winter, are also susceptible. Overcast and polluted atmospheres that block out the sun can also deprive children of vitamin D. Another form of nutritional rickets is seen in extremely premature babies if they are fed a vitamin D–poor formula or if their diet contains inadequate amounts of phosphorus and calcium.
Rickets also can occur due to inherited genetic disorders that result in improper absorption or use of vitamin D, calcium, or phosphorus. In the United States, the most common cause of rickets is a disease called familial hypophosphatemia (hy-po-fos-faTEE-me-uh), which means “too little phosphorus in the blood.” In this genetic disease, phosphorus “leaks” out of the body through the kidneys. However, fewer than 10 out of every 1 million babies are affected by this disease.
Adult rickets, or osteomalacia (os-te-o-ma-LAY-sha), causes bone problems similar to those found in childhood rickets. Osteomalacia can be caused by a nutritional deficiency of vitamin D, but it most commonly occurs when the body has problems absorbing phosphorus and calcium due to other illnesses (such as liver and kidney disease). In some instances, drugs that interfere with absorption of vitamin D cause rickets and osteomalacia.
Children with rickets may not have any symptoms, or they may feel pain and develop bone deformities. A child who has or is developing rickets may experience muscle cramps, twitches, and abnormal contractions of the hands and feet due to low levels of calcium in the blood. The muscles, limbs, and abdomen grow weak, and the bones of the skull remain soft. An infant with rickets may have difficulty developing such basic movement skills as sitting, crawling, and walking due to weakness and pain.
Osteomalacia can cause similar effects: soft bones, skeletal pain, muscular weakness, and susceptibility to fractures.
Rickets can be diagnosed with blood tests, in which the amounts of calcium, phosphorus, and vitamin D are measured, and with x-rays. Nutritional rickets is treated with dietary supplements of vitamin D and calcium. If treated early enough, there will be no long-lasting effects. If untreated, a child may develop permanent bone deformities. Dietary supplements of vitamin D, calcium, and phosphate also may be prescribed for people with rickets caused by other diseases or by genetic defects.
Rickets can be prevented by consuming a diet rich in vitamin D as well as by spending time in the sun. A good source of vitamin D is vitamin D–fortified milk.
See also Broken Bones (Fractures) • Dietary Deficiencies • Growth and Growth Disorders • Kidney Disease
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* ultraviolet is a wavelength of light beyond visible light; on the spectrum of light, it falls between the violet end of visible light and x-rays.
* formula is a prepared, nutritious drink or a dry drink mix designed