NORD gratefully acknowledges Etienne Leveille, MD Candidate, McGill University School of Medicine, and Adjunct Professor Kebashni Thandrayen, Pediatric Endocrinologist, Department of Pediatrics, Chris Hani Baragwanath Acadaemic Hospital, South Africa, for assistance in the preparation of this report.
Vitamin-D deficiency rickets, a disorder that becomes apparent during infancy or childhood, is the result of insufficient amounts of vitamin D in the body. The deficiency of vitamin D may be caused by poor nutrition, a lack of exposure to the sun, or malabsorption syndromes in which the intestines do not adequately absorb nutrients from food. Vitamin D is needed for the metabolism of calcium and phosphorus in the body. Vitamin D affects how calcium is deposited in the bones; thus it is considered essential for proper bone development and growth. Major symptoms of vitamin D deficiency rickets include bone deformities and bone pain, slow growth, fractures and seizures. It can be efficiently treated with vitamin D supplementation and with additional calcium supplementation in some cases. This disorder is rare in developed countries but is not uncommon in certain areas of the world with predisposing factors such as poor sun-exposure, high altitude, and breastfeeding.
Rickets typically manifests in infants and toddlers, but can also happen in older children. Symptoms of vitamin D deficiency rickets include restlessness, lack of sleep, slow growth, a delay in crawling, sitting or walking, soft skull bones (craniotabes), swelling of the skull (frontal bossing), bead-like nodules where the ribs and their cartilages join (rachitic rosary), and a delay in the closing of the skull bones. Aches, pains and enlarged bones are possible, along with swelling at the joints such as wrists and ankles.
Untreated vitamin D deficiency rickets results in the ends of the long bones becoming enlarged and the legs becoming bowed or knock-kneed. Muscles can become weak and the chest may become deformed due to the pull of the diaphragm on the ribs that have been weakened by rickets (Harrison’s groove). Abnormal development and decay of teeth may also occur.
In the more severe, untreated cases of this disorder, the bones may become fragile and fractures may easily occur. Muscle twitching and sharp bending of the wrist and ankle joints (tetany spasms) may also be present.
Some children also develop heart disease (cardiomyopathy) that can be fatal. Occasionally, when there is too little calcium in the blood (hypocalcemia) due to the lack of vitamin D, intellectual disability and seizures (hypocalcemic seizures) may occur.
Vitamin D deficiency rickets can be caused by a lack of vitamin D in the diet, a lack of exposure to the sun, or malabsorption syndromes such as celiac disease, in which there is an inability of the intestines to adequately absorb nutrients from foods. Nursing mothers may have low levels of vitamin D and feed their baby with milk that is deficient in vitamin D.
Vitamin D is required for the metabolism of calcium and phosphorus. Therefore, low levels of vitamin D in turn decrease calcium and/or phosphate levels in the body. This causes a delay in the formation of bone at sites where bone usually grows (delay in bone mineralization in the growth plate).
In some cases, rickets can be initially caused by calcium deficiency alone (hypocalcemia) due to low dietary intake of calcium. Low levels of calcium increase vitamin D utilization and can deplete vitamin D levels, causing a combination of calcium deficiency and vitamin D deficiency or insufficiency rickets.
Vitamin D deficiency rickets affects males and females equally. Even though it can affect older children, rickets mostly affects infants and preschool children and can be present at birth (congenital) in babies born to a woman with low levels of vitamin D.
Nutritional rickets is more common in babies that are breastfed for more than a year, as many women of child-bearing age have low levels of vitamin D and breastmilk is low in vitamin D. This is especially the case for veiled women, as they tend to have low sun exposure. Rickets is also more common in children with darker skin, as they absorb less vitamin D from sunlight, and also in immigrants, refugees, and prematurely born babies.
Rickets is more common in regions of Asia where there is pollution and a lack of sunlight and/or low intake of meat due to a vegetarian diet. The Middle East is a region where Vitamin D deficiency rickets is prevalent due to lack of exposure to the sun because of cultural practices (purdah). Rickets is also more common in Africa, partly because people tend to have darker skin, which reduces vitamin D absorption.
In children, the suspected joints are X-rayed and characteristic changes in the bones may be detected. Blood tests might also reveal high levels of parathyroid hormone (PTH) and alkaline phosphatase (ALP), and low levels of calcium, phosphorus and 25(OH)D (a marker for vitamin D levels).
Treatment of vitamin D deficiency rickets is accomplished with doses of vitamin D given daily until the bone disease is cured. The dose of vitamin D can then be reduced to the daily recommended requirements. Adequate dietary calcium intake also has to be ensured.
In cases where vitamin D deficiency is caused by calcium deficiency, calcium supplementation for at least six months can cure rickets and promote bone healing.
In more severe cases of vitamin D deficiency rickets when cramps, seizures, muscle twitching and sharp bending of the ankle and wrist joints (tetany) is present, the treatment with vitamin D is supplemented with intravenous calcium gluconate.
In some instances, surgery may be required to correct the severe bowing or knock-knee deformities of the legs.
Vitamin D deficiency rickets can be prevented by providing a normal balanced diet to infants and children, assuming that they are exposed to adequate amounts of sun. Fortification of food such as milk with vitamin D and vitamin D supplementation in pregnant women can also prevent rickets.
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