Definition of Rickets

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Rickets: A disease of infants and children that disturbs normal bone formation (ossification). Rickets is a failure to mineralize bone. This softens bone (producing osteomalacia) and permits marked bending and distortion of bones. Up through the first third of the 20th century, rickets was largely due to lack of direct exposure to sunlight or lack of vitamin D. Sunlight provides the necessary ultraviolet rays. These rays do not pass through ordinary window glass. Once the role of vitamin D in rickets was discovered, cod liver oil (which is rich in vitamin D) became a favored, if not too tasty, remedy. Thanks to such supplements of vitamin D, nutritional rickets has become relatively rare in industrialized nations. It still occurs, for example, in breast-fed babies whose mothers are underexposed to sunlight and in dark-skinned babies who are not given vitamin D supplements. And in unindustrialized countries, vitamin D deficiency rickets continues to be a problem. Rickets in North America and Europe now is usually not nutritional.

It is due to other causes, namely:

• Disorders that create vitamin D deficiency by interfering with the absorption of vitamin D through the intestines.
• Diseases (for example, of the liver or kidney) that impair the normal metabolic conversion and activation of vitamin D.
• Conditions that disrupt the normal balance in the body (the homeostasis) between calcium and phosphorus.

No matter what causes rickets, the features are the same. They include softness of the infant's skull (formally known as craniotabes and informally as "Ping-Pong ball skull"), enlargement of the front end of the ribs (creating the "rachitic rosary"), thickening of the wrists and ankles, lateral curving of the spine (scoliosis) and abnormal forward-backward curving of the spine (kyphosis and lumbar lordosis), and deforming and narrowing of the pelvis (which in the female interferes later with delivering vaginally). As the child begins to walk, the weight on the soft shafts of the legs results in knock-knees or, more often, bowlegs. The deformities of the spine, pelvis and legs reduce height leading to short stature. The deformities of the spine impair posture and gait. A person with rickets seemed to walk in a shaky or tottering way so "rickety" came to mean just that, shaky and tottering. The word "rickets" is probably a corruption of "rachitis" which came from the Greek "rhachis" (spine) + the suffix -"itis" (inflammation). Before the causes of rickets were discovered, rickets (which is also called "rachitis") was believed to be an inflammatory disease of the spine.