Rickets is a disease of the growing bones where defective mineralization occurs in both bone and cartilage of the epiphyseal growth plate. The condition is associated with biochemical abnormalities, bone deformities, developmental delays, impaired growth, and sometimes even seizures, particularly in the late course of the disease.
Rickets is a potentially devastating condition, as affected children can experience delays in learning to walk, fractures, and crippling deformities. Furthermore, this disease dramatically increases the risk of pneumonia, which is a condition that contributes significantly to childhood mortality in developing regions of the world.
Rickets, Causes, Signs and Symptoms, Diagnosis and Treatment.
Pathogenesis and types of rickets
Vitamin D has a major impact on skeletal growth and health. Any disturbance in its production, absorption, or metabolism is paramount in the development of rickets. Moreover, insufficient vitamin D concentrations often result in decreased intestinal absorption of calcium.
Even a slight decrease in serum calcium concentrations that can ensue stimulates the secretion of parathyroid hormone, which, in turn, mobilizes calcium and phosphorus from the bones in order to restore serum concentrations to normal levels. When a mineral deficiency occurs at the growth plate, growth slows and bone age is retarded.
Nutritional rickets results either from insufficient sunlight exposure or inadequate intake of dietary vitamin D, calcium, or phosphorus. This type of disease continues to be problematic among infants in many communities, namely among those who are exclusively breastfed.
Type I of vitamin D–dependent rickets is the result of a defective gene that codes for the production of renal 25(OH)D3–1-α-hydroxylase. On the other hand, type II of vitamin D–dependent rickets represents a rare autosomal disorder caused by mutations in the vitamin D receptor.
Rickets refractory to vitamin D treatment is usually caused by a heritable form known as vitamin D–resistant rickets or familial hypophosphatemic rickets. Furthermore, various medical conditions such as malignancies, renal osteodystrophy, and malabsorption syndromes, as well as the use of various medications, can cause rickets.
Impaired growth, as well as bone pain or tenderness in the arms, legs, pelvis, and spine, are commonly observed signs and symptoms of rickets. Bone fractures are also increased in patients with this disease. Dental deformities include the delayed formation of teeth, defects in the structure of teeth, holes in the enamel, and increased incidence of dental caries.
Characteristic skeletal deformities include bowed legs or knock knees (genu varum and genu valgum, respectively), asymmetrical or odd-shaped skull, costochondral swelling (also known as the rachitic rosary), as well as cranial, pelvic, and spinal deformities (with scoliosis or kyphosis in the latter group).
A semicoronal impression, which is also known as Harrison's groove, is sometimes seen over the abdomen at the level of the insertion of the diaphragm, which results from pulling on the weakened ribs by the diaphragm during inspiration. The sternum may project anteriorly and appear prominent (pectus carinatum or pigeon breast).
Clinical presentation of rickets is similar around the world, but the age of presentation and the risk of hypocalcemic symptoms, such as tetany or uncontrolled muscle spasms, can vary significantly depending on the age of presentation and the relative importance of vitamin D deficiency (when compared to calcium in different populations.
In areas where vitamin D deficiency is more commonly observed, rickets typically presents during the first year of life, often with clinically-significant hypocalcemia. On the other hand, calcium deficiency accounts for much of the prevalent nutritional rickets in Africa, thus the disease usually presents from the second year of life with infrequently observed hypocalcemic tetany.