Bone is made up of two substances: the organic collagen portion and the inorganic mineral portion. The inorganic portion of bone is made up of both calcium and phosphate. Rickets describes the softening and weakening of children’s bones. While rickets looks the same on X-rays, there are many different types. These types depend on which mineral is deficient (low) – either calcium, phosphorus, or the enzyme that helps create the mineral portion of bone.
The most common reason for a calcium deficiency in bone is a lack of Vitamin D, and not a lack of calcium in the diet. Vitamin D is a hormone that allows the body to absorb calcium.
If you don’t have enough vitamin D, then the body cannot take in calcium. If the body does not have enough calcium in the blood, it will take the calcium out of bone. If this cycle continues, the bone becomes weaker as the deficit in calcium grows. As a result, the child can develop signs of rickets.
The main reason for a phosphorus deficiency in bone is an inherited disorder known as X-linked hypophosphatemic rickets. This is the most commonly inherited rickets in the United States, occurring in 1 out of every 20,000 births. Girls are twice as likely as boys to have this disorder.
The defect can be found in the PHEX gene. Normally, the kidney sends phosphates to the bone through the blood. The defect causes the kidney to get rid of the phosphate instead of sending it through the blood, leading to an overall phosphorus shortage in the blood.
Similar to low calcium in the blood, when the body recognizes that there is not enough phosphorus in the blood, it will remove it from the bone instead. It is also believed that the genetic defect prevents the kidneys from making the mature forms of Vitamin D, which are necessary for the body to absorb calcium.
When there is less calcium and/or phosphorus, the bone and the growth plate of bone become weaker. This weakening can lead to growth delay. In more severe cases, children suffer from seizures from calcium deficiencies or fractures from weakened bone.
Treatment depends on which mineral is deficient. Determining treatment may require the assistance of an endocrinologist. Once the deficiency is known, treatment involves replacing the mineral – whether it be calcium, vitamin D, phosphorus or a combination of these minerals. In many cases, the bone changes are reversible. In more severe cases, children may continue to have growth delays and crooked. Occasionally, bones become so crooked that they may require surgery for correction.