Signs and symptoms of rickets can include:

• Delayed growth
• Delayed motor skills
• Pain in the spine, pelvis and legs
• Muscle weakness

Because rickets softens the areas of growing tissue at the ends of a child's bones (growth plates), it can cause skeletal deformities such as:

• Bowed legs or knock knees
• Thickened wrists and ankles
• Breastbone projection

Your child's body needs vitamin D to absorb calcium and phosphorus from food. Rickets can occur if your child's body doesn't get enough vitamin D or if his or her body has problems using vitamin D properly. Occasionally, not getting enough calcium or lack of calcium and vitamin D can cause rickets.

Lack of vitamin D

Children who don't get enough vitamin D from these two sources can develop a deficiency:

• Sunlight. Your child's skin produces vitamin D when it's exposed to sunlight. But children in developed countries tend to spend less time outdoors. They're also more likely to use sunscreen, which blocks the sun's rays that trigger the skin's production of vitamin D.
• Food. Fish oil, egg yolks and fatty fish such as salmon and mackerel contain vitamin D. Vitamin D has also been added to some foods and beverages, such as milk, cereal and some fruit juices.

Problems with absorption

Some children are born with or develop medical conditions that affect the way their bodies absorb vitamin D. Some examples include:

• Celiac disease
• Inflammatory bowel disease
• Cystic fibrosis
• Kidney problems

Factors that can increase a child's risk of rickets include:

• Dark skin. Dark skin has more of the pigment melanin, which lowers the skin's ability to produce vitamin D from sunlight.
• Mother's vitamin D deficiency during pregnancy. A baby born to a mother with severe vitamin D deficiency can be born with signs of rickets or develop them within a few months after birth.
• Northern latitudes. Children who live in geographical locations where there is less sunshine are at higher risk of rickets.
• Premature birth. Babies born before their due dates tend have lower levels of vitamin D because they had less time to receive the vitamin from their mothers in the womb.
• Medications. Certain types of anti-seizure medications and antiretroviral medications, used to treat HIV infections, appear to interfere with the body's ability to use vitamin D.
• Exclusive breast-feeding. Breast milk doesn't contain enough vitamin D to prevent rickets. Babies who are exclusively breast-fed should receive vitamin D drops.

Left untreated, rickets can lead to:

• Failure to grow
• An abnormally curved spine
• Bone deformities
• Dental defects
• Seizures