Osteomalacia is softening of the bones due to a lack of vitamin D or a problem with the body's ability to break down and use this vitamin.

The softer bones seen in persons with osteomalacia have a normal amount of collagen, which gives the bones its structure, but lack the proper amount of calcium.

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

Other conditions that may lead to osteomalacia include:

• Not enough vitamin D in the diet
• Not enough exposure to sunlight, which produces vitamin D in the body
• Malabsorption of vitamin D by the intestines

Use of very strong sunscreen, limited exposure of the body to sunlight, short days of sunlight, and smog are factors that reduce formation of vitamin D in the body. The elderly and those who avoid drinking milk are at increased risk for osteomalacia.

Other conditions that may cause osteomalacia include:

• Cancer
• Hereditary or acquired disorders of vitamin D metabolism
• Kidney failure and acidosis
• Liver disease
• Phosphate depletion associated with not enough phosphates in the diet
• Side effects of medications used to treat seizures