Rickets is more prevalent in developing countries. Unlike developing countries, the United States was able to eradicate the nutritional form of the disease in the 1930s after discovering that vitamin D supplementation prevented it. Today, however, surveillance for the disease is largely absent. Therefore, it is impossible to know the prevalence of the disease in the United States.
Rickets is a disease that occurs during childhood, as a result of the failure of growing bones to mineralize. These changes are evidenced by many radiographic and skeletal changes. There is typically a build-up of unossified cartilage as well as the lack of calcified osteoid. However, there are reported cases of rickets presenting in adolescents, particularly as a result of nutritional vitamin D deficiency. In infants, rickets is caused by vitamin D deficiency as well as a lack of exposure to sunlight.
The disease is an example of severe vitamin D deficiency. The peak incidence of the disease is between 3-18 months of age. The deficiency usually occurs before the disease becomes obvious upon physical examination. The deficiency may then present with hypocalcemic seizures, lethargy, failure of growth, and irritability.
The symptoms of rickets present as bone pain and tenderness in the spine, pelvis, legs, and arms. In addition, children with rickets often present with a number of skeletal abnormalities. These include bowing of the legs or knocked knees, soft fontanels, and frontal bossing. Delayed tooth eruption may also occur, as well as an increased frequency of dental carries. Severe muscle weakness is a common sign of rickets. The more serious consequences of the disease include grand mal seizures and infections of the upper respiratory tract.
Other signs and symptoms of rickets are restlessness and irritability and head sweating. The head of infants with rickets are somewhat square, with open fontanels and frontal bossing. Craniotabes, or soft osseous borders, are also present. Enlargement of costochondral junctions may also be observed. In addition, the muscles may be flabby and anemia may be present. Carpal pedal spasms may occur, as well as hypocalcemic seizures.
In adolescents or adults with rickets or, alternatively, osteomalacia, overt skeletal signs are absent. However, these patients complain of aching, throbbing bone discomfort that gets worse when lying in bed or sitting down.
The exact causes of bone discomfort and muscle weakness are unknown, but they are believed to be associated with vitamin D deficiency.
The causes of rickets depend on the type of rickets. In nutritional rickets, inadequate intake of vitamin D, phosphorus, or calcium, as well as inadequate exposure to sunlight, are the primary causes. Although the disease is uncommon in the United States, it can still occur when infants are exclusively breastfed, has limited exposure to the sun, or is dark-skinned. Dark-skinned individuals require more exposure to sunlight compared to lighter-skinned persons to produce relatively the same amount of vitamin D. This is because melanin in the skin absorbs solar radiation and acts as a neutral filter. Aside from this, a diet dependent solely on non-fortified milk that lacks calcium can also lead to rickets. Nutritional rickets presents during the first two years of life with developmental delay, gait abnormality, and failure to thrive.
On the other hand, vitamin D-dependent rickets develops secondary to a defect in the genes that code for the production of renal hydroxylase.
Vitamin D-resistant rickets is caused by mutations of on the X chromosome, particularly of the phosphate-regulating gene.
The primary risk factor for developing rickets is the lack of vitamin D in the diet and lack of exposure to sunlight. However, children who are deprived of adequate levels of calcium also develop rickets. The primary cause of this is that a diet poor in calcium increases parathyroid hormone (PTH) levels, and subsequently leads to hyperphosphaturia.
Intake of high levels of aluminum is another risk factor for rickets. Aluminum is commonly administered to patients with chronic kidney disease to block phosphate absorption in the form of antacids. Since aluminum is a trivalent cation, at high concentrations it inhibits the release of PTH. It inhibits osteoblastic activity. It is also deposited on the surface of bones, thus preventing mineralization of the osteoid.
At high concentration, fluoride stimulates osteoblastic activity. However, it also gets incorporated as calcium fluoride hydroxyapatite crystals into the skeleton. Coupled with low-calcium diets, this can lead to skeletal deformities.
A wide variety of drugs can also lead to the development of rickets. Usually, children who are placed on anticonvulsants are at risk for developing rickets. Glucocorticoids, which are drugs used to treat HIV can also cause rickets. Herbal preparations, such as St. John’s Wort, can lead to vitamin D deficiency.
Rickets may have severe complications. It is strongly associated with pneumonia in children, particularly in developing countries. In addition, it is also associated with an increased risk of mortality, where the risk of death is one in seven as compared to children without rickets. If the pelvis in women is deformed, this leads to difficulties associated with labor along with morbidity related to childbirth.
The person’s gait may be permanently affected by rickets. Bowing of the legs may be permanent. Children may develop kyphosis, which may be permanent as well.
The diagnosis of rickets depends on gathering the infant’s history. The infant’s gestational age, the degree of exposure to sunlight, and diet should be assessed by the physician. The dietary history should include specifics of calcium and vitamin D intake. In addition, the family history should also be gathered. A family history of orthopedic abnormalities, short stature, alopecia, poor dentition, and parental consanguinity may be signals of inherited rickets.
The review of systems should focus on orthopedic as well as growth concerns. The signs and symptoms of hypocalcemia should be elicited, such as numbness, muscle cramps, tetany, paresthesia, and seizures. Complete dental and physical examination should be conducted in children suspected of having rickets. The entire skeleton should be palpated to search for points of tenderness.
Serum levels of calcium, alkaline phosphatase, phosphorus, PTH, urea nitrogen, calcidiol, and creatinine may be investigated through laboratory examinations. Urine studies may include urinalysis to determine the levels of phosphorous and calcium.
An anteroposterior radiograph of the child may also be taken, particularly of rapidly-growing areas, such as the knees or wrists. Radiographic findings such as a widening of the distal physis, angular deformities, and widening and fraying of the metaphysis are suggestive of rickets.
Surgery may be required to repair bony abnormalities caused by rickets. However, nutritional and metabolic imbalances have to be corrected in order for optimal healing to occur. Nutritional rickets is treated with supplementation of vitamin D, phosphorous, and calcium.
Various preparations of vitamin D, administration routes, and dosing schedules are available. Ergocalciferol (Calciferol) is a drug that is useful in children. It is usually administered through injections or orally in the liquid of capsule form. The capsules can be softened in water, or they can be mixed with tasty food, such as applesauce. Oral doses or intramuscular injections of vitamin D (150,000 to 600,000 IU) in patients as young as 3 months has been found to be effective in treating rickets.
The outlook for children with rickets is excellent, especially if the disease is diagnosed early on. In long-standing and severe cases of the disease, however, bowing of the legs can be permanent. In some cases, these may resolve without surgical intervention.
Preventing rickets depends primarily on educating family members about the importance of vitamin D supplementation and sunlight exposure. For expectant mothers, education includes recommending prenatal vitamins. Nutritional counseling for expectant mothers is also recommended.
Vitamin D deficiency is defined as serum 25 (OH)D that is less than 20 ng/mL. Usually, physicians recommend that levels above 30 ng/mL be consumed in order to maximize intestinal calcium absorption as well as to reduce the circulating PTH levels. In order to achieve this, it is necessary to acquire 1000 to 2000 IU of vitamin D on a daily basis.
The American Academy of Pediatrics recommends that all infants receive vitamin D at a dose of 400 IU per day. This is the optimal dose to prevent rickets in children and infants. Adequate calcium intake should also be recommended to mothers, which is defined as 800 mg per day for children under 12 years of age, 1,300 mg for adolescents, and 1000 mg for adults.
In order to address the phosphorous deficiency, sodium phosphate should be taken in amounts of 250-500 mg 3-5 times a day. This should be taken along with 1,25(OH)D (calcitriol) at a dose of 0.5-1.0 mg twice a day. The key is to maintain the balance between phosphate and calcium in order to achieve mineralization of the osteoid.
Increasing exposure to sunlight, especially in dark-skinned children, should also prevent rickets. Rickets can easily be prevented if there are education and supplementation.