Rickets | Research & Encyclopedia Articles

Rickets

Rickets (or rachitis) is a bone disorder primarily caused by a deficiency of vitamin D during a child's prime bone-growing years. The lack of vitamin D seriously affects the body's ability to absorb and use calcium, the mineral most necessary for the proper growth, development, and hardening of bone. Without sufficient calcium, the child's bones grow more slowly, become weaker, and tend to bend more easily. Because the weight-bearing bones are most seriously affected, the child's legs and pelvis may be misshapen--sometimes to a crippling degree.

Lack of sunlight also appears to contribute to the severity of rickets because, normally, the body can produce its own vitamin D from fatty precursor substances--but only in the presence of sunlight.

Although known for centuries, rickets became an increasingly serious problem in the industrial age, reaching its peak in the nineteenth century and the early part of the twentieth century. As late as the 1920s, rickets affected millions of children around the world. Interestingly, because of the major role played by sunlight in helping to counter its severity, rickets was especially prevalent in the largest and most highly industrialized cities--cities where small children either stayed indoors or played in smog-covered streets in the shadows of tall buildings. In 1921, for example, a survey found that at least half the children admitted to hospitals in New York City were affected to some degree by rickets.

Without knowing its true cause, physicians could diagnose the disorder easily enough but found it almost impossible to treat. In 1922, however, Elmer McCollum and his coworkers produced evidence that cod-liver oil contained a specific chemical that could both prevent rickets and help counter its effects. McCollum not only identified the chemical but named it vitamin D. (At roughly the same time, the cause of rickets was also established by Edward Mellanby (1884-1955) and Harriet Click in England.)

Finally in possession of an effective remedy for rickets, physicians and public health officials promptly began distributing a variety of fish-liver oils to affected children and the epidemic was soon curbed. A few years later, when vitamin D began to be added routinely to milk and other widely used foods, primary rickets became a rare disorder in virtually all developed countries.

Less common causes of rickets include dietary calcium deficiency, phosphate deficiency, and hypophosphatasia. "Hypophosphatemia," or "Vitamin D Resistant Rickets," is an extremely rare genetic disease (estimates suggest it affects from one to 10 of every one million births) which occurs even in the presence of sufficient vitamin D and afflicts more males than females. In this disease, tiny channels within the kidney fail to resorb phosphate.