What is rickets?

Rickets is a disorder in which the growing bones of an infant or child have abnormally low levels of calcium and phosphorous, causing them to become weak and soft. This can lead to permanent deformities of the skeleton and teeth, failure to grow properly, muscle weakness, seizures, and chronic pain. Although the effects are sometimes irreversible, most types of rickets can be prevented by ensuring that the child has enough vitamin D in their diet and gets enough sun exposure. This is because vitamin D is essential for bones to mineralize or harden; and because sun exposure is one of the ways the body produces vitamin D. Although this condition is relatively rare in developed countries, it is quite common in undeveloped countries.

Four main types

There are four main types of rickets and a number of highly specific subtypes. The main ones are:

  • nutritional rickets : This is one of the most common types and is caused by a dietary deficiency of vitamin D, calcium, phosphorus, or all three.
  • Vitamin D resistant rickets : Also called X-linked hypophosphatemia, this is a genetic condition thought to be caused by a defect in the kidneys. Children with this condition make too much phosphate, which makes it hard for bones to harden. Unlike other types, this is usually not related to a vitamin D deficiency.
  • Vitamin D dependent rickets : There are two subtypes of this condition, called Type I and Type II. Type I is a genetic condition in which a mutation in a certain gene causes the body to be unable to convert a substance called calcifediol into calcitriol, the active form of vitamin D. Type II is also genetic and is caused by a mutation that produces from the cells of the body to be unable to recognize calcitriol.
  • congenital rickets : This is a condition where a baby is born with the disorder because the mother has a vitamin D deficiency or osteomalacia, the adult version of rickets.

Other more specific types include renal osteodystrophy, drug-induced rickets, hepatobiliary rickets, and hypervitaminosis D rickets. The reason there are so many specific types of this condition is that many different problems can cause the body to not absorb or process vitamin D, calcium or phosphorus correctly. All types of this condition can usually be diagnosed by a blood test and sometimes by a urine test. Doctors may also take X-rays or do a bone density scan to see how damaged your bones and teeth are.

signs

The main signs of this condition are skeletal deformities, including:

  • Swollen wrists: This is often one of the first signs.
  • Bowed legs, particularly in children over the age of three, or knocking at the knees.
  • The fontanel or "soft spot" on a baby's head takes a long time to harden.
  • An expelled chest caused by a protruding breastbone, sometimes called a "pigeon chest."
  • Necklace-shaped bumps along the ribs sometimes called rickety rosary.
  • A curved column.
  • Brittle bones, easily breakable.

Other signs include abnormally short stature or failure to grow at a normal rate; muscular weakness; chronic pain; and problems with the teeth, including holes in the teeth and abnormally smooth teeth. Sometimes children with this condition also have seizures.

Causes

The underlying cause of this condition is a problem with the body absorbing or processing calcium or phosphorous, two minerals that are essential for bones to grow properly. A vitamin D deficiency can cause many of these problems, since the body needs vitamin D to absorb calcium and phosphorous from food. This is why the two main risk factors for rickets are a nutritional deficiency of vitamin D and insufficient exposure to sunlight, as the body can make some vitamin D on its own if it absorbs sunlight . Certain genetic conditions can also cause the body to be unable to absorb or process vitamin D, phosphorous, or calcium properly, which can also lead to this condition.

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Generally speaking, children are most at risk of developing this condition when they are between six and 24 months of age, due to how quickly their bones grow during this time. Another risk factor for this condition includes having dark skin, as darker pigmented skin produces less vitamin D when exposed to sunlight. Children who live in areas that are not usually very sunny are at greater risk of this condition than those who live in sunny places. Some anti-seizure medications also seem to be related to this condition.

Certain health conditions can also put a child at risk for this condition, including cystic fibrosis, kidney-related problems, and digestive disorders such as celiac disease, lactose intolerance, or inflammatory bowel disease. Chronic or prolonged malnutrition, diarrhea or vomiting are also risk factors. All of these risk factors are related to how the body processes or absorbs vitamin D. For example, children with a kidney condition called renal tubular acidosis sometimes cannot absorb vitamin D normally, or those with long-term diarrhea term they may not be able to extract or store enough vitamin D from food before it leaves the body. People with lactose intolerance often do not consume enough vitamin D products, putting them at risk of deficiency.

There are also lifestyle factors that can put children at risk, including:

Prevention and treatment:

Many types of rickets can be prevented and treated by making sure the child has enough vitamin D in their diet and gets enough sunlight. It's important to have both components, as it's hard for the body to get enough vitamin D from just one.

Ways to get vitamin D into a child's diet include

Children should also be allowed to play outside in the sun without sunscreen for at least 15 to 30 minutes a day so their skin can absorb enough sunlight.

These steps may not be enough for children with certain genetic types of rickets, particularly vitamin D-resistant rickets. In those with Type I vitamin deficiency rickets, doctors often recommend giving children high levels of specific types of vitamin D supplements. However, it is important to do this only under a doctor's supervision, as feeding children a large amount of vitamin D can lead to a condition called hypercalcemia, where the blood has too much calcium. This can cause vomiting, constipation, muscle weakness, and abdominal pain, among other things. Type 2 vitamin D deficiency rickets does not respond well to standard vitamin D supplementation, but can sometimes be treated with calcitriol, the active, concentrated form of vitamin D, and calcium supplements.

There are also ways to treat the bone deformities that accompany this condition. Some skeletal deformities correct themselves after a child receives treatment, but children and adults can also wear braces and maintain proper posture to counteract bow legs and spinal complications. In severe cases, surgery may be the only way to correct the deformities.

Videos

Video 1 – A video with information about this condition and vitamin D supplementation, including X-ray images.

Video 2 - A technical video on bone formation in children with this condition.

Additional Resources

www.medicinenet.com – An overview of the condition, including images and quizzes.

http://emedicine.medscape.com – More information on this condition, including its history, pathophysiology, and epidemiology.

www.thachers.com - Images of the symptoms of this condition.

www.wheelessonline.com - More information on vitamin D resistant rickets.

www.ncbi.nlm.nih.gov: An overview of causes, symptoms, diagnosis, and complications.

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