Rickets is a disease of bone 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 skeletal (bone) deformities.
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What Is Vitamin D?
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 also can be obtained from food. Vitamin D is added to milk and infant formulas, and egg yolks, liver, cod-liver oil, and other fish oils are good dietary sources of vitamin D.
What Is Rickets?
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.
Nutritional Childhood Rickets
Rickets can occur because of a nutritional deficiency in vitamin D. Today 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, also are 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.
a Vitamin D Time-Line
- During the 1700s, cod-liver oil and sunlight were recognized as effective treatments for rickets.
- By 1918, scientists had discovered vitamins. Experiments on animals showed that cod-liver oil had a vitamin that helped prevent rickets.
- By 1924, ultraviolet (UV) light was used for treating rickets. The process was called irradiation. Researchers understood that vitamin D was formed by the effects of ultraviolet rays on the skin.
- Between 1930 and 1931, scientists in England and Germany were able to produce pure vitamin D for the first time.
Genetic Childhood Rickets
Rickets also can occur because of inherited genetic disorders that result in improper absorption or utilization 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-fa-TEE-me-a), which means too little phosphorus in the blood. This is a genetic disease in which phosphorus "leaks" out of the body through the kidneys. However, fewer than 10 out of every 1 million babies are affected by this disease.
Other Types of Rickets
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 vita-min D, but it most commonly occurs when the body has problems absorbing phosphorus and calcium because of other illnesses (such as liver and kidney disease). In some instances, drugs that interfere with absorption of vitamin D cause rickets and osteomalacia.
What Are the Symptoms of Rickets?
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 movements as sitting, crawling, and walking due to weakness and pain.
The type of bone deformity caused by rickets depends on the age at which the disease develops. If it begins before the walking stage, the spine may be abnormally curved. If it begins or continues after the child starts to walk, the legs may become bowed by the weight of the body. For children with rickets, the teeth take more time to grow in, and often the wrists and ankles are thickened. Because of weak bones, children with rickets also are susceptible to fractures.
Osteomalacia can cause similar effects: soft bones, skeletal pain, muscular weakness, and susceptibility to fractures.
How Is Rickets Diagnosed and Treated?
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.
How Is Rickets Prevented?
Rickets can be prevented by eating 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.
Mavarra, Tova. Encyclopedia of Vitamins, Minerals, and Supplements. New York: Facts on File, 1996.
Tamborlane, William. Yale Guide to Children's Nutrition. New Haven: Yale University Press, 1997.