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Rickets is the softening and weakening of bones in children, usually because of an extreme and prolonged vitamin D deficiency.

Vitamin D is essential in promoting absorption of calcium and phosphorus from the gastrointestinal tract, which children need to build strong bones. A deficiency of vitamin D makes it difficult to maintain proper calcium and phosphorus levels in your bones.

Your body senses an imbalance of calcium and phosphorus in your bloodstream and reacts by taking calcium and phosphorus from your bones to raise blood levels to where they need to be. This softens or weakens the bone structure, resulting most commonly in skeletal deformities such as bowlegs or improper curvature of the spine. Osteomalacia is the adult version of rickets.

If a vitamin D or calcium deficiency causes rickets, adding vitamin D or calcium to the diet generally corrects any resulting bone problems for the child. Rickets due to a genetic condition may require additional medications or specialized treatment. Some skeletal deformities caused by rickets may need corrective surgery.

Vitamin D deficiency begins months before physical signs and symptoms of rickets appear. When rickets symptoms develop, they may include:

• Skeletal deformities. These include bowed legs, abnormal curvature of the spine, pelvic deformities and breastbone projection in the chest.
• Fragile bones. Children with rickets are more prone to bone fractures.
• Impaired growth. Delayed growth in height or limbs may be a result of rickets.
• Dental problems. These include defects in tooth structure, increased chance of cavities, poor enamel and delayed formation of teeth.
• Bone pain. This includes dull, aching pain or tenderness in the spine, pelvis and legs.
• Muscle weakness. Decreased muscle tone may make movement uncomfortable.

Vitamin D acts as a hormone to regulate calcium and phosphorus levels in your bones. You absorb vitamin D from two sources:

• Sunlight. Your skin produces vitamin D when it's exposed to sunlight. This is the most common way for most adolescents and adults to produce the vitamin.
• Food. Your intestines absorb vitamin D from the foods you eat or from supplements or multivitamins you may take.

In the past, dietary vitamin D deficiency was the most common cause of rickets in the United States. Now, with the increased use of vitamin supplements and the variety of foods fortified with vitamin D (such as orange juice and breakfast cereals), vitamin D deficiency cases of rickets have fallen.

Currently in the United States, conditions that impair vitamin D absorption such as the surgical removal of all or part of the stomach (gastrectomy) and celiac disease, in which the small intestine doesn't absorb certain nutrients from food, cause most cases of rickets.

Other causes of rickets include:

• Hereditary rickets (X-linked hypophosphatemia), an inherited form of rickets caused by the inability of the kidneys to retain phosphorus, or a complication of renal tubular acidosis, a condition in which your kidneys are unable to excrete acids into urine
• Lack of exposure to sunlight, which stimulates the body to make vitamin D

Children 6 to 24 months old are most at risk of rickets because they're growing rapidly, and vitamin D, calcium and phosphorus play a major role in the growth process.

Risk factors for rickets include:

• Lack of vitamin D. Breast-fed infants who don't receive supplemental vitamin D are at increased risk of developing rickets. While exposure to sunlight could produce the necessary amounts of vitamin D, sunburn and skin cancer are real dangers for young children. Sunscreens also markedly decrease vitamin D production.
• Lack of calcium and phosphorus. Children who don't get enough calcium and phosphorus in their diets are at increased risk of rickets. The availability of milk and other products that contain these minerals make this cause a rarity for rickets in the United States and other developed countries.

Your doctor or your child's doctor may diagnose rickets by:

• Physical examination. Your doctor will check if the pain or tenderness is coming directly from the bones, instead of the joints and muscles surrounding them.
• Blood tests. These measure calcium and phosphorus levels to see if they're normal.
• X-rays. Your doctor may take images of affected bones to look for softening or weakness.
• Medical history. Kidney problems, celiac disease or diagnosis of a sibling with rickets may help lead your doctor to a rickets diagnosis.

While easily treated once it's diagnosed, rickets has a severe list of complications if left untreated. Untreated vitamin D deficiency rickets may lead to:

• Delays in your child's motor skills development
• Failure to grow and develop normally
• Increased susceptibility to serious infections
• Skeletal deformities
• Chronic growth problems that can result in short stature (adults measuring less than 5 feet tall)
• Seizures
• Dental defects

The aim of treatment for rickets is to solve the underlying disorder. If deficiencies in vitamin D, calcium or phosphorus are at fault, replacing vitamin D and those minerals generally eliminates the signs and symptoms of rickets, such as bone tenderness and muscle weakness. Improvement may occur within weeks.

Your doctor may prescribe a vitamin D supplement or ask you to increase your intake of vitamin D-fortified foods, including fortified breakfast cereal, orange juice, fish and processed milk. Your doctor may also recommend that you get a little sun. Remember that moderate exposure is the safest, and don't expose infants under 6 months to direct sunlight.

Getting a sufficient intake of calcium is crucial to maintaining healthy bones. Your doctor can suggest an appropriate level of calcium intake depending on your age and whether you have absorption problems. The combination of increased vitamin D intake with calcium may be enough to eliminate the effects of rickets entirely.

Treating complications
For some cases of bowlegs or spinal deformities, your doctor may suggest special bracing to position your child's body appropriately as the bones grow. More severe skeletal deformities may require surgery.

Although most adolescents and adults receive much of their necessary vitamin D from exposure to sunlight, infants and young children need to avoid direct sun entirely or be especially careful by always wearing sunscreen.

Vitamin D supplements
In light of these factors, and because human milk contains only a small amount of vitamin D, the American Academy of Pediatrics recommends that all breast-fed infants receive 200 international units (IU) of oral vitamin D daily beginning during the first two months of life and continuing until the daily consumption of vitamin D-fortified formula or milk is two to three glasses or 500 milliliters (mL).

Vitamin D supplements for infants generally come in droplet form. Use only supplements that contain up to 400 IU of vitamin D per mL or tablet. Avoid supplements containing a higher concentration of vitamin D (some forms come in levels of up to 8,000 IU/mL), because they're unsafe for children.

Getting enough calcium
Calcium and phosphorus consumption are also important for bone formation in childhood. Breast milk is the best source of calcium during a child's first year of life. Most commercially available formulas also meet calcium requirements. Because of these factors, infants in the United States generally achieve 100 percent of their recommended intake of calcium. Unfortunately, this trend stops as children grow into adolescents and adults, and many fail to take in enough calcium, an essential component of skeletal formation. This lack of calcium may lead to osteomalacia, a form of rickets in adults.

Recommended daily intake of calcium is as follows (serving sizes vary with age):

• 1 to 3 years of age. 500 milligrams (mg) (two servings of dairy products a day)
• 4 to 8 years of age. 800 mg (two to three servings of dairy products a day)
• 9 to 18 years of age. 1,300 mg (four servings of dairy products a day, as most bone mass production occurs during this period)
• 19 to 50 years of age. 1,000 mg a day (three servings of dairy products a day)

Milk accounts for three-fourths of the calcium in the food supply of the United States. If you're not drinking milk, be sure to find another source. Remember that low-fat can still mean high-calcium. Other sources of calcium include leafy green vegetables (spinach), fortified orange juices, fortified breakfast cereals and calcium supplements.