Osteomalacia

Definition

Osteomalacia involves softening of the bones caused by a deficiency of vitamin D or problems with the metabolism of this vitamin.

Causes, incidence, and risk factors

There are numerous causes of osteomalacia. In children, the condition is called rickets and is usually caused by a deficiency of vitamin D.

Conditions that may lead to osteomalacia include:

• Inadequate dietary intake of vitamin D
• Inadequate exposure to sunlight (ultraviolet radiation), which produces vitamin D in the body
• Malabsorption of vitamin D by the intestines

Other conditions that may cause osteomalacia include:

• Hereditary or acquired disorders of vitamin D metabolism
• Kidney failure and acidosis
• Phosphate depletion associated with low dietary intake of phosphates
• Kidney disease or cancer (rare)
• Side effects of medications used to treat seizures

Use of very strong sunscreen, limited exposure of the body to sunlight, short days of sunlight, and smog are factors that decrease formation of vitamin D within the body.

Risk factors for osteomalacia are related to the causes. In the elderly, there is an increased risk among people who tend to remain indoors and those who avoid milk because of lactose intolerance.

Symptoms

• Diffuse bone pain, especially in the hips
• Muscle weakness
• Bone fractures with minimal trauma

Symptoms associated with low calcium including:

• Numbness around the mouth
• Numbness of extremities
• Spasms of hands or feet
• Abnormal heart rhythms

Signs and tests

• A bone biopsy shows osteomalacia.
• Serum vitamin D level may be low.
• Serum calcium levels vary with the cause of the disorder.
• Serum phosphate levels vary with the cause of the disorder.
• A bone X-ray may show features of osteomalacia.
• A bone mineral density scan (DEXA) may show reduced bone mineral density.

Other tests may be done to determine renal problems or other underlying disorders. They include:

• PTH
• Calcium (ionized)
• ALP (alkaline phosphatase) isoenzyme

Treatment

Oral supplements of vitamin D, calcium and phosphorus may be given depending on the underlying cause of the disorder. Larger doses of vitamin D and calcium may be needed for people with intestinal malabsorption.

Monitoring of blood levels of phosphorus and calcium may be indicated for people with certain underlying conditions.

Expectations (prognosis)

Improvement in the condition of the bones, evidenced by bone X-rays, can be seen within a few weeks in some people with vitamin deficiency disorders. Complete healing with treatment takes place in 6 months.

Complications

Recurrence of symptoms is a possible complication.

Calling your health care provider

Call for an appointment with your health care provider if you have symptoms of osteomalacia, or if you think that you may be at risk for this disorder.

Prevention

An adequate dietary intake of dairy products that are fortified with vitamin D and exposure of the body to sunlight can prevent osteomalacia caused by vitamin D deficiency in adults.

Illustrations

Diseased hip

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