Osteomalacia In Children

A disorder involving softening and weakening of the bones of children, primarily caused by lack of vitamin D and/or lack of calcium or phosphate.

Alternative names: osteomalacia in children; deficiency - vitamin D; renal osteodystrophy; pediatric osteomalacia; vitamin D deficiency; renal rickets

The pathogenesis of nutritional rickets is not well-understood. While the etiologies include deficiencies of vitamin D, calcium (Ca) or phosphate (PO4), and perhaps aluminium toxicity, the role these nutrients play in the development of tissue level anomalies characteristic of rachitic cartilage and bone has yet to be defined.

Rickets is a disorder caused by insufficiency or inefficient action of activated vitamin D in the body during childhood, a lack of vitamin D in the diet or with malabsorption disorders characterized by poor fat absorption, including steatorrhea, sprue, and short bowel syndrome. Vitamin D is a fat-soluble vitamin that may be absorbed from the intestines or may be produced by the skin when the skin is exposed to ultraviolet light (particularly sunlight).It is converted to its active form by the body in 2 steps, occurring first in the liver and completed in the kidneys. In its active form, vitamin D acts as a hormone to regulate calcium absorption from the intestine and to regulate levels of calcium and phosphate in the bones. Active vitamin D is assisted by the actions of other body hormones.

Because vitamin D is fat soluble, conditions that reduce digestion or absorption of fats will decrease the ability of vitamin D to be absorbed from the intestines. Sunlight is important to skin production of vitamin D, and environmental conditions where sunlight exposure is limited may reduce this source of vitamin D. Lack of vitamin D production by the skin may occur with indoor confinement or working indoors during the daylight hours, or it may occur in climates with little exposure to sunlight.

When the body is deficient in vitamin D, it is unable to properly regulate calcium and phosphate levels. If the blood levels of these minerals becomes low, the other body hormones may stimulate release of calcium and phosphate from the bones to the bloodstream.

Rickets is a bone disease of children. It causes progressive softening and weakening of the bone structure. There is a loss of calcium and phosphate from the bone, which eventually causes destruction of the supportive matrix. The parathyroid gland may increase functioning to compensate for decreased levels of calcium in the bloodstream, resulting in even more loss of calcium and phosphorous as it is reabsorbed from the bones. In severe cases, cysts may develop in the bones.

Rickets is fairly rare. It is most likely to occur during periods of rapid growth where the body demands high levels of calcium and phosphate. It is usually seen in young children 6 to 24 months old and is uncommon in newborns.

A dietary lack of vitamin D may occasionally occur in people on a vegetarian diet who do not drink milk products or in people who are lactose intolerant (those who have trouble digesting milk products). A dietary lack of calcium and phosphorous may also play a part in nutritional causes of rickets. Rickets from a dietary lack of these minerals is rare because calcium and phosphorous are present in milk and green vegetables. A dietary lack of calcium causes osteoporosis (an adult disorder causing brittle bones) more often than it causes rickets.

Hereditary rickets is a vitamin D-resistant form of rickets caused when the kidney is unable to retain phosphate. It is an inherited, sex-linked disorder.

Rickets may also be caused by kidney disorders involving renal tubular acidosis. The acidic condition of the body causes the calcium in the bones to dissolve, leaving soft, weak bones.

Occasionally, rickets may be caused in children with disorders of the liver or biliary (liver secretion) system, when fats and vitamin D are inadequately absorbed or when the vitamin D is not converted to its active form.

Renal osteodystrophy occurs in people with chronic renal failure. The manifestation is virtually identical to that of rickets in children, and that of osteomalacia or osteoporosis in adults.

Symptoms include:

  • Bone pain or tenderness - arms, legs, spine, pelvis
  • Skeletal deformities - bowlegs, forward projection of the breastbone (pigeon chest), "bumps" in the rib cage ("rachitic rosary"), asymmetrical or odd-shaped skull, spine deformities (spine curves abnormally, including scoliosis or kyphosis), pelvic deformities
  • Increased tendency toward bone fractures
  • Dental deformities
  • Delayed formation of teeth - defects in the structure of teeth, holes in the enamel, painful teeth, aching aggravated by sweets, or by cold/hot food or drinks, increased incidence of cavities in the teeth (dental caries)
  • Fever, especially at night
  • Restlessness, especially at night
  • Weakness, progressive - decreased muscle tone (loss of muscle strength), decreased muscle development
  • Muscle cramps
  • Impaired growth - short stature (adult is less than 5 feet tall), slow (child 0-5 years)
  • Pectus excavatum
  • Sutures - separated

The treatment goals are the relief of symptoms and the correction of the cause. The replacement of deficient calcium, phosphorous, and/or vitamin D causes symptoms to disappear. There may be a need to use the biologically active form of vitamin D in people who have vitamin D-resistant rickets or who have difficulty converting vitamin D to its active form. Dietary sources of vitamin D include fish, liver, and processed milk. Exposure to moderate amounts of sunlight is encouraged. The underlying cause must be treated to prevent recurrence. Maintaining good posture helps to correct skeletal deformities. Positioning or bracing may be used to reduce or prevent deformities. A surgical correction of some skeletal deformities may be necessary.

Rickets may be avoided by maintaining an adequate intake of calcium, phosphorous, and vitamin D. This may require dietary supplements in people with associated gastrointestinal or other disorders.

Renal causes of vitamin D should be treated promptly. Levels of calcium and phosphorous should be monitored regularly in people with renal disorders.

Vitamin D requirements have been difficult to measure. The main source of the vitamin is endogenous: 7-dehydrocholesterol converts to vitamin D in the skin after exposure to sunlight and heat. The diet is a much less important source, especially if the skin is regularly exposed to sunlight.

Under certain circumstances there may be a definite risk of vitamin D deficiency. For example, in the far north, especially during the winter, production of vitamin D may be decreased because of the insufficient exposure of the skin to sunlight. Production may be further compromised in people with increased skin pigmentation.

The consumption of human milk is considered another risk factor for vitamin D deficiency, although rickets does not develop in most breast-fed infants. The concentration of vitamin D in human milk has been reported to be as low as 20 IU/L, much less than the recommended 400 IU/d; however, levels vary considerably and can be influenced by maternal intake. Indeed, Hollis showed that concentrations could increase up to 20 times if the mother received adequate vitamin D supplementation.

Supplementation with vitamin D during pregnancy, breast-feeding and infancy is therefore desirable. However, there is still conflicting evidence regarding the adequacy of 400 IU/d of vitamin D in northern populations.

Experience in the United States over several decades showed that a daily intake of 400 IU could prevent rickets, promote growth and maintain normal calcium and phosphorus levels without any evidence of toxicity.

Infants who are entirely breast-fed should be given 400 IU/d of vitamin D. This amount may be increased to 800 IU/d during the winter for children living in the far north. The administration of 800 IU/d should be limited to children less than 2 years of age, who are at greatest risk for rickets.

Infants who are bottle-fed with formulas made from fortified whole or canned milk have sufficient amounts of vitamin D during the summer but should receive a supplement of 400 IU/d of vitamin D during the winter.

Pregnant women and nursing mothers in the north should take 400 IU/d of vitamin D either as fortified milk or in addition to their vitamin and mineral supplementation, which provides 400 IU/d of vitamin D.

Children more than 2 years of age who do not drink adequate amounts of milk enriched with vitamin D should be given 400 IU/d of vitamin D during the winter. The long days during the summer should provide enough sunlight to produce adequate amounts of endogenous vitamin D.

Because there are still questions regarding the risks and benefits of giving 800 IU/d to people in high-risk groups, research into vitamin D requirements in northern latitudes should be encouraged.

If rickets is not corrected while children are still growing, skeletal deformities and short stature may be permanent, but if it is corrected while the child is young skeletal deformities often reduce or disappear with time.

See also: Osteomalacia

The nutrients mentioned above reflect the major nutritional supplements that may help the condition. Please do remember however that nutritional supplementation is an adjunct to medical treatment and in no way replaces medical treatment.

- Hollis B.W.: Individual quantitation of vitamin D2, vitamin D3, 25-hydroxyvitamin D in human milk. Anal Biochem 1983; 131: 211-219

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