- 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 produce too much phosphate, which makes it difficult for bones to become hard. Unlike other types, this is not usually connected to a deficiency of vitamin D.
- 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 the mutation of a certain gene makes the body not able 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 makes some of the body's cells to not able to recognize calcitriol.
- Congenital Rickets — this is a condition in which a baby is born with the disorder because of the mother having 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 generally be diagnosed through a blood test, and sometimes through a urine test. Doctors may also take X-rays or do a bone density scan to see how damaged the bone and teeth are.
The main signs of this condition are skeletal deformities, including:
- Thickened wrists — this is often one of the first signs.
- Bowed legs, particularly in children over three years old, or knock knees.
- The fontanelle or “soft spot” on a baby's head taking a long time to harden.
- A pushed-out chest caused by a protruding breast-bone, sometimes called a “pigeon chest.”
- Necklace-like bumps along the ribs sometimes called a rachitic rosary.
- A curved spine.
- Fragile, easily breakable bones.
Other signs include an abnormally short stature, or a failure to grow at a normal rate; muscle weakness; chronic pain; and problems with teeth, including holes in teeth and abnormally soft teeth. Sometimes children with this condition also have seizures.
The underlying cause of this condition is a problem with the body absorbing or processing calcium or phosphorus, two minerals that are essential for bones to grow properly. A deficiency of vitamin D can cause many of these problems, since the body needs vitamin D to absorb calcium and phosphorus from foods. This is why the two main risk factors for rickets are a nutritional deficiency of vitamin D, and not enough exposure to sunshine, since the body can make some vitamin D on its own if it absorbs sunshine. Certain genetic conditions can also cause the body to not be able to absorb or process vitamin D, phosphorus, or calcium correctly, which can also lead to this condition.
Generally speaking, children are most at-risk for developing this condition when they are between six and 24 months old, because of how fast their bones grow during this time. Another risk factor for this condition include having dark skin, since darker pigmented skin produces less vitamin D when exposed to sunshine. Children living in areas that are typically not very sunny are at a higher risk for this condition than those who live in sunny places. Some anti-seizure medications also appear to be connected with this condition.
Certain health conditions can put also a child at risk for this condition, including cystic fibrosis, problems related to the kidneys, and digestive disorders like celiac disease, lactose intolerance or inflammatory bowel disease. Chronic or long-term malnutrition, diarrhea, or vomiting are also risk factors. All of these risk factors are related to the way vitamin D is processed or absorbed by the body. For instance, children with a kidney condition called renal tubular acidosis are sometimes unable to absorb vitamin D normally, or those with long-term diarrhea may not be able to extract or store enough vitamin D from food before it passes out of the body. Those with lactose intolerance often don't consume enough products with vitamin D in them, leaving them at risk for deficiency.
There are also lifestyle-related factors that can put children at risk, including:
- Feeding the child a strict vegetarian or vegan diet without supplementing for vitamin D.
- Not letting the child get enough sunshine: this sometimes happens accidentally by making the child wear powerful sunscreen on a continuous basis, or by having the child continuously veiled for religious reasons.
- Breastfeeding the child exclusively or for an extended time. This is because human breast milk does not have enough vitamin D for a growing child. Pediatricians advise women who wish to feed their children entirely with breast milk or to breastfeed for extended periods of time to supplement the child's diet with vitamin D drops.
Prevention and Treatment:
Many types of rickets can be prevented and treated by making sure that the child has enough vitamin D in his or her diet and gets enough sunshine. It's important to have both of these components, since it's hard for the body to get enough vitamin D by either one alone.
Ways to incorporate vitamin D into a child's diet include
- Making sure the child drinks enough milk, particularly vitamin D fortified milk, and other dairy products.
- Incorporating other vitamin D-rich foods into the child's diet, including fortified cereals, eggs, mushrooms, and some fish, including sockeye salmon, sardines, and herring.
- Supplementing with vitamin D drops or pills under a doctor's supervision. This is particularly important for children on a vegan or vegetarian diet or for children who are fed only with breast milk.
Children should also be allowed to play outside in the sun without sunscreen for at least 15 to 30 minutes a day so that the skin can absorb enough sunshine.
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. It is important to only do this under the supervision of a doctor though, as feeding children a lot of vitamin D can lead to a condition called hypercalcemia, where the blood has too much calcium. This can lead to vomiting, constipation, muscle weakness, and abdominal pain, among other things. Type 2 vitamin D deficiency rickets does not respond well to normal vitamin D supplementation, but can sometimes be treated with calcitriol, the concentrated, active form of vitamin D, and calcium supplements.
There are also ways to treat the bone deformities that come along with this condition. Some skeletal deformities correct themselves after the child receives treatment, but children and adults can also wear braces and maintain proper posture to counteract bowed legs and spinal complications. In severe cases, surgery may be the only way to correct deformities.
Video 1 — A video with information about this condition and vitamin D supplementation, including pictures of X-rays.
Video 2 — A technical video about the formation of bone in children with this condition.
www.medicinenet.com — An overview of the condition, including pictures and quizzes.
http://emedicine.medscape.com — More information about this condition, including its history, pathophysiology and epidemiology.
www.thachers.com — Pictures of the symptoms of this condition.
www.wheelessonline.com — More information about vitamin D resistant rickets.
www.ncbi.nlm.nih.gov — An overview with causes, symptoms, diagnosis, and complications.