Rickets is the softening and weakening of bones in children, often because of an extreme and prolonged vitamin D or calcium deficiency. Rare inherited problems also can cause rickets.

Vitamin D helps a child's body absorb calcium and phosphorus from food. Not enough vitamin D makes it hard to maintain proper calcium and phosphorus levels in bones, which can cause rickets.

Adding vitamin D or calcium to the diet generally corrects the bone problems associated with rickets. When rickets is due to another underlying medical problem, your child may need additional medicines or other treatment. Some skeletal deformities caused by rickets may require corrective surgery.

Rare inherited disorders related to low levels of phosphorus, the other mineral component in bone, may require other medicines.

Symptoms of rickets can include:

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

In infants, symptoms of rickets may be harder to identify because bone and muscle complaints are often not detected until a child starts to walk. Symptoms of rickets in infants caused by low blood calcium levels may include:

• Tight muscle tone.
• Breathing sounds that are not regular.

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

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

Talk to your healthcare professional if your child develops bone pain, muscle weakness or obvious skeletal deformities. If you are concerned your infant isn't getting enough vitamin D, especially if they have risk factors for vitamin D deficiency such as darker skin pigmentation or exclusive breastfeeding, talk to your healthcare professional.

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 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 also are 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 also has 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 problems 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:

• Darker skin pigmentation. Brown or Black 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 serious vitamin D deficiency can be born with symptoms 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.
• Medicines. Certain types of anti-seizure medicines and antiretroviral medicines, used to treat HIV infections, appear to interfere with the body's ability to use vitamin D.
• Exclusive breastfeeding. Breast milk doesn't contain enough vitamin D to prevent rickets. Babies who are exclusively breastfed typically receive vitamin D drops.

If not treated, rickets can lead to:

• Failure to grow.
• Bone deformities.
• Dental defects.
• Seizures.

Exposure to sunlight provides the best source of vitamin D. During most seasons, 10 to 15 minutes of exposure to the sun near midday is enough. But if you have brown or Black skin, if it's winter, or if you live in northern latitudes, you might not be able to get enough vitamin D from sun exposure.

In addition, because of skin cancer concerns, infants and young children, especially, are warned to avoid direct sun or to wear sunscreen and protective clothing.

To prevent rickets, make sure your child eats foods that contain vitamin D naturally — fatty fish such as salmon and tuna, fish oil, and egg yolks — or that have been fortified with vitamin D, such as:

• Infant formula.
• Cereal.
• Bread.
• Milk, but not foods made from milk, such as some yogurts and cheese.
• Orange juice.

Check labels to determine the vitamin D content of fortified foods.

If you're pregnant, ask your healthcare professional about taking vitamin D supplements.

Guidelines recommend that all infants should receive 400 international units (IU) a day of vitamin D. Because human milk contains only a small amount of vitamin D, infants who are exclusively breastfed should receive supplemental vitamin D daily. Some bottle-fed infants also may need vitamin D supplements if they aren't receiving enough from their formula.

During the exam, the healthcare professional typically will gently press on your child's bones, checking for irregularities. They may pay specific attention to the following:

• Skull. Babies who have rickets often have softer skull bones and might have a delay in the closure of the soft spots, called fontanels.
• Legs. While even healthy toddlers are a little bowlegged, an exaggerated bowing of the legs is common with rickets.
• Chest. Some children with rickets develop changes in their rib cages, which can flatten and cause their breastbones to protrude.
• Wrists and ankles. Children who have rickets often have larger or thicker wrists and ankles.

Diagnosing rickets in babies can be challenging. Rickets may be harder to identify as bone and muscle changes often are not detected until a child starts to walk. Your healthcare professional likely will pay attention to if your baby is growing well, has regular breathing sounds and has typical muscle tone.

For children of all ages, X-rays of the affected bones can reveal bone deformities. Blood and urine tests can confirm a diagnosis of rickets and also monitor the progress of treatment.

Most cases of rickets can be treated with vitamin D and calcium supplements. Follow the directions as to dosage. Too much vitamin D can be harmful.

Your child's healthcare team may check your child's progress with X-rays and blood tests.

If your child has a rare inherited disorder that causes low amounts of phosphorus, supplements and medicines may be prescribed.

For some cases of bowleg or spinal deformities, your healthcare professional might suggest special bracing to position your child's body properly as the bones grow. More-serious skeletal deformities might require surgery.

You'll likely start by seeing your primary care professional or a pediatrician. Depending on the cause of your child's symptoms, you might be referred to a specialist.

Here's information to help you get ready for your appointment.

What you can do

Before your appointment, make a list of:

• Your child's symptoms, including any that might not seem related to the reason you made the appointment, and note when they started.
• Key personal information, including medicines and supplements your child takes and whether anyone in your immediate family has had similar symptoms.
• Information about your child's diet, including food and drinks your child usually consumes.

What to expect from your doctor

Your healthcare team might ask some of the following questions:

• Is your baby getting vitamin D supplements?
• How often does your child play outdoors?
• Does your child wear sunscreen?
• At what age did your child start walking?
• Has your child had much tooth decay?