Rickets

Rickets

A bone abnormality of childhood. The term refers to a group of disorders in which there is a defect in the mineralization of bone matrix or osteoid. In adults, the disorder is referred to as OSTEOMALACIA, as the defect occurs only in the matrix and the growth plates have already sealed. In children, the disorder is referred to as rickets because the mineralization abnormality is located at the growth plate. Rickets is often classified as calcium- or phosphate-deficient rickets.

The major skeletal problems are seen at sites in the body where there is rapid bone growth, such as in the forearm, knee, and the costochondral junctions. Thus, the child with rickets may have bone abnormalities, such as a bowing of the legs and the wrists. Abnormalities may also be seen at the ends of ribs, such as a beading known as rachitic rosary.

Rickets can cause growth abnormalities as well as be associated with abnormalities of nerve and muscle function, depending on the cause. Children with severe metabolic abnormalities have bone pain, sweat excessively, and are more prone to developing infections.


Vitamin D-Dependent Rickets

Type 1 and type 2 rickets are caused by rare congenital errors of vitamin D metabolism. With type 1 rickets, there is a defect in the enzyme in the kidney
that coverts vitamin D stores to its most active form. Children with type 1 rickets typically have symptoms in their first two years of life. Calcium and 2,5-dihydroxyvitamin D levels are low, while, parathyroid hormone levels are elevated. Large doses of vitamin D preparations are used to treat this condition.
In children with type 2 rickets, the children are resistant to the effects of vitamin D. Their vitamin D blood levels are normal or elevated. This disorder is usually diagnosed in children before they reach age two. Rarely, this condition has been diagnosed in adults. Very large doses of vitamin D are needed by patients to correct their low calcium levels and to lead to normal bone mineralization.


Hypophosphatemic Rickets

Another form of rickets is hypophosphatemic rickets.
This disorder causes an abnormal reabsorption of phosphorus from the kidneys. Typically, male children are affected. They present with growth problems, low blood phosphorus levels, and lowerleg abnormalities. The abnormal gene that causes this disorder has been named PHEX. There have been rare reports of females with a mild form of this disorder. Growth hormone has been effectively
used with patients to improve growth, although these children are not growth hormone deficient.