Alternate Names: Osteomalacia in children; Deficiency - Vitamin D; Renal osteodystrophy; Pediatric osteomalacia; Vitamin D deficiency; Renal rickets

Causes and Risks:

Rickets is a disorder caused by insufficiency or inefficient action of activated Vitamin D in the body during childhood. 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.

Nutritional causes of rickets occur with a lack of Vitamin D in the diet or with malabsorption disorders characterized by poor fat absorption, including steatorrhea, sprue, and short bowel syndrome.

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.

Prevention: 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.

Symptoms:

• 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)
  • Growth, slow (child 0-5 years)
• Pectus excavatum
• Sutures - separated

Signs and Tests: A musculoskeletal examination reveals tenderness or pain of the bone itself, rather than joints or muscles. In some cases, tetany (prolonged muscle spasm) may occur if serum levels of calcium are low. Chvostek’s sign may be positive (a spasm of facial muscles with tapping over the facial nerve) indicating low serum levels of calcium.

• Serum calcium and serum phosphorus may be low.
• Serum alkaline phosphatase may be high.
• Arterial blood gases may reveal metabolic acidosis.
• Bone X-rays may show decalcification or changes in the shape or structure of the bones.
• A bone biopsy is rarely performed, but will confirm rickets.

• A PTH
• A calcium; urine
• A calcium (ionized)
• ALP (alkaline phosphatase) isoenzyme

Treatment:

The treatment goals are the relief of symptoms and the correction of the cause. The replacement of deficient calcium, phosphorous, 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.

Prognosis: The disorder may be corrected with replacement of deficient minerals and Vitamin D. Laboratory values and X-rays usually improve after about 1 week, although some cases may be resistant and require large doses of minerals and Vitamin D.

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.

Complications:

• Chronic skeletal pain
• Skeletal deformities
• Skeletal fractures, may be spontaneous (without a cause such as trauma)

Call your health care provider if symptoms indicating rickets may be present.