Rickets is a disease of growing bone that is unique to children and adolescents. It is caused by a deficiency or impaired metabolism of vitamin D, magnesium, phosphorus or calcium. It leads to softening and weakening of the bones.
Rickets is among the most frequent childhood diseases in many developing countries. The predominant cause is a vitamin D deficiency, but lack of adequate calcium in the diet may also lead to rickets .
Types of Rickets
Different types have been described and may include:
- Nutritional Rickets
- Vitamin D Resistant Rickets
- Vitamin D Dependent Rickets
- Congenital Rickets
Pathophysiology
Vitamin D deficiency rickets occurs when the metabolites of vitamin D are deficient. Less commonly, a dietary deficiency of calcium or phosphorus may also produce rickets. Vitamin D-3 (cholecalciferol) is formed in the skin from a derivative of cholesterol under the stimulus of ultraviolet-B light. It is converted into the active metabolite calcitriol after final hydroxylation in the kidney. Calcitriol acts to regulate the body’s calcium metabolism by the following mechanisms:
(1) it promotes absorption of calcium and phosphorus from the intestine; (2) it increases reabsorption of phosphate in the kidney; and, (3) it acts on bone to release calcium and phosphate. Calcitriol may also directly facilitate calcification. These actions result in an increase in the concentrations of calcium and phosphorus in extracellular fluid.
This increase of calcium and phosphorus in extracellular fluid, in turn, leads to the calcification of osteoid, primarily at the metaphyseal growing ends of bones but also throughout all osteoid in the skeleton. Parathyroid hormone facilitates the 1-hydroxylation step in vitamin D metabolism.
In the vitamin D deficiency state, hypocalcemia develops, which stimulates excess secretion of parathyroid hormone. In turn, renal phosphorus loss is enhanced, further reducing deposition of calcium in the bone.
Etiology
The body needs vitamin D to absorb calcium and phosphorus from food. Rickets can occur if thechild’s body doesn’t get enough vitamin D or if his or her body has problems using vitamin D Continue reading »
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This is a non-inflammatory deformity of the femoral head caused by a vascular insult leading to osteonecrosis of the capital femoral epiphysis.
