Rickets

What is rickets?

Rickets is a disorder in which there is softening and weakening of the bones of children, primarily caused by the lack of vitamin D or calcium and phosphate. It is most likely to occur during periods of rapid growth when the body requires high levels of calcium and phosphate. It is usually seen in young children 6 to 24 months old and is uncommon in newborns.

What is the cause?

Infants in their first year are mainly affected due to an inadequate intake of vitamin D because of the low content of this vitamin in both human and animal milk and the failure to provide them with a supplement of vitamin D in any form.

Vitamin D is a fat-soluble vitamin that is absorbed from the intestines or may be produced by the skin when the skin is exposed to ultraviolet light (particularly sunlight). It is converted to its active form by the body in 2 steps, first in the liver and completed in the kidneys. In its active form, vitamin D acts as a hormone to regulate calcium absorption from the intestine and to regulate levels of calcium and phosphate in the bones. Active vitamin D is assisted by the actions of other body hormones. Since vitamin D is fat soluble, conditions that reduce digestion or absorption of fats will decrease the absorption of vitamin D to be absorbed from the intestines. Sunlight is important for the production of vitamin D in the skin, and environmental conditions where sunlight exposure is limited may reduce this source of vitamin D. This happens when children are confined indoors, or it may occur in climates with little exposure to sunlight. When the body is deficient in vitamin D, it is unable to properly regulate calcium and phosphate levels. If the blood levels of these minerals becomes low, the other body hormones may stimulate release of calcium and phosphate from the bones to the bloodstream.

A dietary lack of vitamin D, calcium and phosphorus may occasionally occur in people on a vegetarian diet, who do not take milk products or in people who are lactose intolerant (those who have trouble digesting milk products).
Hereditary rickets is a vitamin D-resistant form of rickets caused when the kidney is unable to retain phosphate. It is an inherited, sex-linked disorder. Rickets may also be caused by kidney disorders. The acidic condition of the body causes the calcium in the bones to dissolve, leaving them soft and weak.

Occasionally, rickets may be caused in children with disorders of the liver or biliary (liver secretion) system, when fats and vitamin D are inadequately absorbed or when the vitamin D is not converted to its active form.

What are the symptoms?

Rickets is a bone disease of children. It causes progressive softening and weakening of the bone structure. The infant with rickets has often received sufficient calories and may appear well nourished, but is restless, fretful, pale, with flabby muscles. The abdomen is distended. He is prone to respiratory infections and gastrointestinal upsets. Development is delayed; the teeth often erupt late and there is failure to sit, stand, crawl and walk at the normal ages. The bone changes are the most characteristic signs of rickets.
Symptoms may include:

• Bone pain or tenderness
  
• Skeletal deformities
  
• Increased tendency toward bone fractures
  
• Dental deformities
  
• A slight fever and restlessness at night
  
• Weakness, progressive decreased muscle tone (loss of muscle strength) and decreased muscle development.
  
• Muscle cramps
  
• Impaired growth
  
• In severe cases, cysts may develop in the bones
  
• In addition to the above symptoms, a child with rickets may have bowlegs and develop a pigeon breast and a protruding stomach.

How is it diagnosed?

A musculoskeletal examination reveals tenderness or pain of the bone itself, rather than joints or muscles. If the physician suspects osteomalacia or rickets, a blood test may be done to measure the amounts of the minerals, calcium and phosphorus. X-rays of the affected bones must be obtained. Bone X- rays may show decalcification or changes in the shape and structure of the bones.

What is the treatment?

The treatment of rickets is to provide a supplement of vitamin D and calcium. The replacement of deficient calcium, phosphorus and vitamin D relieves the symptoms. It may be necessary to use the biologically active form of vitamin D in people who have vitamin D-resistant rickets or who have difficulty converting vitamin D to its active form. Dietary sources of vitamin D include fish, liver, and processed milk. Exposure to moderate amounts of sunlight is encouraged. The underlying cause must be treated to prevent recurrence. Maintaining good posture helps to correct skeletal deformities. Positioning or bracing may be used to reduce or prevent deformities.

Surgical correction of some skeletal deformities may be necessary. Laboratory values and X-rays usually improve after about 1 week, although some cases may be resistant and require large doses of minerals and vitamin D. Rickets is not a fatal disease but if it is not corrected while children are still growing, skeletal deformities and short stature may be permanent.

How can rickets be prevented?

Rickets may be avoided by maintaining an adequate intake of calcium, phosphorus and vitamin D. This may require dietary supplements in people with associated gastrointestinal or other disorders. Renal causes of vitamin D should be treated promptly. Levels of calcium and phosphorus should be monitored regularly in people with renal disorders. Mothers must be educated regarding the need to keep their infants and children in the sunshine as much as possible.