rickets(redirected from vitamin D–dependent rickets, type II)
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rachitis(rəkī`tĭs), bone disease caused by a deficiency of vitamin D or calcium. Essential in regulating calcium and phosphorus absorption by the body, vitamin D can be formed in the skin by ultraviolet rays contained in sunlight; it can also be consumed in such foods as fish oils, eggs, and butter. Since calcium and phosphorus are essential for proper development and hardening of bones, the disease manifests itself in children as softening of bones, abnormal bone growth, and enlargement of cartilage at the ends of long bones. Where bones must support weight, such as the legs and pelvis, the skeleton is likely to become bent or deformed. The result is often knock-knees, bowlegs, and deformities of the chest and pelvis. In temperate climates or the tropics, vitamin-D deficiency usually results from poor diet rather than from lack of exposure to ultraviolet rays of sunlight. Rickets is no longer common in developed countries because milk is readily obtained and is usually fortified with vitamin D; infants commonly receive vitamin D as a supplement. Treatment of rickets is largely preventive, i.e., by early recognition and by including adequate amounts of vitamin D and calcium in the diet.
a disease occurring in infancy and early childhood, generally from the age of two months to one year, and caused by deficiency of vitamin D. Its course is marked by impaired metabolism, chiefly of minerals. The disease was first described in 1650 by F. Glisson.
In man. In man, rickets develops when the infant obtains insufficient vitamin D with food and when autosynthesis of this vitamin is impaired owing to insufficient ultraviolet radiation. The disease is more common in winter among artificially fed, premature, and sickly infants. When there is a deficiency of vitamin D, the amount of phosphorus and calcium in the blood decreases, the activity of alkaline phosphatase increases, the amount of citrates in the tissues, blood plasma, and urine decreases, and the amount of amino acids in the urine increases. Hypocalcemia leads to intensification of the function of the parathyroid glands. As a result of these changes, the exchange of calcium between the blood and the bone tissue is disrupted.
The first symptoms of rickets usually appear in infants at the age of about two months, and somewhat later in premature infants. The infant becomes restless and sleep is disrupted. There is sweating, especially of the head, and balding of the occiput. Somewhat later these symptoms are supplemented by a decrease in muscle tone and resultant enlargement of the abdomen (frog-belly). There is softening of the bones of the skull (craniotabes) and of the margins of the fontanel. The junctions of the bony and cartilaginous parts of the ribs thicken (rachitic rosary), the frontal and parietal eminences enlarge, and the head acquires a square shape with an olympian forehead. The ribs become soft and bend easily, and the thorax becomes deformed and laterally constricted (pigeon breast). Rachitic kyphosis develops, and somewhat later there is a deformation of the tubular bones. The epiphyses of the forearm bones and the phalanges of the fingers become thickened (rachitic bracelets and strings of pearls, respectively). The bones of the lower extremities become deformed, with the legs resembling the letter O or the letter X. The pelvic bones almost always become deformed. The time and order of dentition are disrupted. If the disease is not treated, rachitic changes may continue into the second and even the third year of life, and the skeletal deformations may remain for life. Rachitic children manifest poor physical and even mental development. They begin to sit and walk later than healthy children, and are ill more often and more severely, especially with pneumonia.
Rickets is prevented by prenatal care, sufficient fresh air and sunshine, and proper diet. The infant should be breast-fed and beginning at the age of one month should be given fruit, berry, and vegetable juices. Egg yolk should be given at the age of four months, and from the age of 4½ to five months the infant should be given such supplementary foods as vegetable purees and cereal. Massage and exercise are desirable beginning at the age of 1½ months. In winter the child should be exposed to irradiation from a mercury vapor lamp and given vitamin D, citrates, and fish oil. Premature infants are given vitamin D from the age of two weeks. Rickets is treated with vitamin D, citrates, and ultraviolet rays.
REFERENCESSviatkina, K. A., A. M. Khvul’, and M. A. Rassolova. Rakhit. Moscow, 1974.
Tur, A. F. Rakhit. Leningrad, 1966.
Aktual’nye voprosy rakhita. Edited by K. A. Sviatkina. Kazan, 1971.
“Krankheiten des Calcium-und Phosphatstoffwechsels.” In Keller-Wiskott. Lehrbuch der Kinderheitkunde. Stuttgart, 1961.
A. F. TUR
In animals. Rickets may develop in the young of all species of animals, most commonly in pigs and calves. It is caused by insufficient vitamin D in the fodder and by insufficient amounts or incorrect proportions of calcium salts and phosphorus salts. Absence of sunlight and exercise and crowded, dark quarters promote the appearance of rickets. The disease’s earliest manifestations are dystrophy and softening of bone tissue. In the early stages, appetite is impaired. Later symptoms are deformation and curvature of the bones, thickening of the joints, and difficulty of movement. The disease is prevented and treated by proper feeding, ultraviolet irradiation, regular exercise, and proper living conditions. Vitamin D and mineral supplements are administered internally.
REFERENCEVnutrennie nezaraznye bolezni zhivotnykh. Edited by A. M. Kolesov. Moscow, 1972.
N. M. PREOBRAZHENSKII