hypophosphatemic rickets

rickets /rick·ets/ (rik´ets) a condition due to vitamin D deficiency, especially in infancy and childhood, with disturbance of normal ossification, marked by bending and distortion of the bones, nodular enlargements on the ends and sides of the bones, delayed closure of the fontanelles, muscle pain, and sweating of the head.

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adult rickets  osteomalacia.

familial hypophosphatemic rickets  any of several inherited disorders of proximal renal tubule function causing phosphate loss, hypophosphatemia, and skeletal deformities, including rickets and osteomalacia.

fetal rickets  achondroplasia.

hereditary hypophosphatemic rickets with hypercalciuria  a form of familial hypophosphatemic rickets; hypophosphatemia is accompanied by elevated serum 1,25-dihydroxyvitamin D, increased intestinal absorption of calcium and phosphate, and hypercalciuria.

hypophosphatemic rickets  any of a group of disorders characterized by rickets associated with hypophosphatemia, resulting from dietary phosphorus deficiency or due to defects in renal tubular function; skeletal deformities are present but hypocalcemia, myopathy, and tetany are absent and serum parathyroid hormone is normal.

oncogenous rickets  oncogenous osteomalacia occurring in children.

pseudovitamin D–deficiency rickets  vitamin D, sometimes specifically the type I form.

refractory rickets  vitamin D

vitamin D–dependent rickets  either of two (types I and II) inherited disorders characterized by myopathy, hypocalcemia, moderate hypophosphatemia, secondary hyperparathyroidism, and subnormal serum concentrations of 1,25-dihydroxyvitamin D; type I can be overcome by high doses of vitamin D, but type II cannot.

vitamin D–resistant rickets 

1. X-linked hypophosphatemia.

2. any of a group of disorders characterized by rickets but not responding to high doses of vitamin D; most are forms of familial hypophosphatemic rickets.

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hypophosphatemic rickets

[hī′pōfos′fətē′mik]

a rare familial disorder characterized by impaired resorption of phosphate in the kidneys and poor absorption of calcium in the small intestine, which result in osteomalacia, retarded growth, skeletal deformities, and pain. Treatment includes replacement of phosphate and vitamin D, to be taken by mouth.

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rickets [rik´ets]

a condition of infancy and childhood caused by deficiency of vitamin D, which leads to altered calcium and phosphorus metabolism and consequent disturbance of ossification of bone. Because of the widespread use of vitamin D–fortified milk, and the giving of vitamin supplements to most infants, the disease is now uncommon in the United States. (A second disease, clinically indistinguishable from ordinary rickets but resistant to large doses of vitamin D, is called vitamin D–resistant rickets.)

Since the action of sunlight on the skin produces vitamin D in the human body, rickets often occurs in parts of the world where the winter is especially long, or where smoke and fog constantly intercept the sun. Black and other dark-skinned people are somewhat more susceptible to the disease if they live in areas with little sunlight, since the pigment in the skin blocks absorption of the sun's rays. When a vitamin D deficiency occurs in adults, it produces osteomalacia.

Symptoms. A major symptom of rickets is softening (decalcification) of the bones. In children, this can produce various degrees of deformity, including nodules on the ribs and flexibility and bending of bones. Bowleg and knock-knee and an improperly developed or misshapen skull of a squared or boxed appearance are typical. The ability of the bones to support the body is seriously impaired.

Prevention. A proper diet that includes vitamin D–fortified milk is usually sufficient to prevent rickets. Ordinary milk contains adequate amounts of calcium but is a poor source of vitamin D. Small amounts of the vitamin are present in eggs, and in such fish as cod, herring, tuna, sardines, and salmon. Sunlight and other sources of ultraviolet light are beneficial.

Treatment. Treatment of an active case of rickets involves the administration of vitamin D concentrate. The response to treatment usually is rapid.

anticonvulsant rickets rickets occurring in children receiving long-term anticonvulsant therapy; the drugs induce vitamin D deficiency (frequently compounded by dietary insufficiency of the vitamin) and hypocalcemia, hypophosphatemia, and secondary hyperparathyroidism by increasing the rate of conversion of the vitamin to inactive metabolites.

familial hypophosphatemic rickets any of several inherited disorders of proximal renal tubular function causing phosphate loss, hypophosphatemia, and skeletal deformities, including rickets and osteomalacia.

hypophosphatemic rickets any of a group of disorders characterized by rickets associated with hypophosphatemia, resulting from dietary phosphorus deficiency (antacid-induced osteomalacia) or due to defects in renal tubular function, either hereditary (familial hypophosphatemic rickets) or acquired. While skeletal deformities (e.g., bowleg, short stature) are present, neither hypocalcemia, myopathy, nor tetany occur, and serum parathyroid hormone is normal.

vitamin D–dependent rickets, type I an autosomal recessive disorder of rickets with myopathy, hypocalcemia, moderate hypophosphatemia, secondary hyperparathyroidism, and subnormal serum concentrations of 1,25-dihydroxyvitamin D. The disorder can be overcome by high doses of vitamin D or physiologic doses of calcitriol.

vitamin D–dependent rickets, type II an autosomal recessive disorder similar to type I but with elevated serum concentrations of 1,25-dihydroxyvitamin D. The disorder cannot be overcome by high levels of vitamin D or its metabolites and is believed to be due to defective receptor binding, absence of the receptors, or post-receptor defects. Multiple variants exist, subdivided as those with or without alopecia.

vitamin D–resistant rickets a condition almost indistinguishable from ordinary rickets clinically but resistant to unusually large doses of vitamin D; it is often familial but may occur sporadically. In hypophosphatemic vitamin D–resistant rickets, hypophosphatemia is the main characteristic, while in hypocalcemic vitamin D–resistant rickets, the serum concentration of phosphate is within normal limits or nearly so, and the concentration of calcium is abnormally low.