Nutritional Diseases

CASE 8: Osteomalacia

Clinical History:

A 65-year-old woman lives alone in a small trailer in a trailer park. She is living off of pension benefits and meager savings, but the rent takes most of her income. She eats sparingly, mostly just sandwiches with bread and cheese, and some canned soup. She doesn't go out much, mostly to Friday night bingo. She gets little exercise. She incurred a fracture to her right wrist in a fall several months ago. After an open reduction-internal fixation (ORIF) procedure, the fracture is still not completely healed. She now has medical care costs to pay, too.

  1. What do you suspect?

  2. Decreased bone mass, from osteoporosis or osteomalacia, are the possibilities. The more common of the two is osteoporosis, but since this group session deals with nutritional deficiencies, we will concentrate on the latter.

  3. Is there laboratory testing that is of value?

  4. There are no specific laboratory findings with osteoporosis. There are two markers of osteoblastic activity that may be abnormal with osteomalacia. In osteomalacia from vitamin D deficiency, bone-specific alkaline phosphatase may be elevated because of enhanced osteoblastic activity, whereas the vitamin D dependent osteocalcin may be decreased.

    In reality, bone densitometry is performed as the "gold standard" to determine the degree of bone loss (the findings radiographically are identical for osteoporosis and osteomalacia). If one suspected a potential dietary deficiency, give the patient vitamin D and calcium supplements and do another bone densitometry measurement in several months. You would do this anyway to determine the rate of bone loss if osteoporosis were suspected. If the bone loss is dietary, then the supplements should improve the situation.

  5. What does this dietary deficiency cause in children?

  6. Vitamin D deficiency in children causes rickets. Since the growing bones are not properly mineralized, then there is deformity, particularly with long bones, which can become bowed, with widened epiphyses.

  7. What are dietary sources?

  8. Milk in the United States is fortified with 10 micrograms (400 IU) of vitamin D per quart , and rickets is now uncommon in the US. One cup of vitamin D fortified milk supplies about one-fourth of the estimated daily need for this vitamin in adults. Although milk is fortified with vitamin D, dairy products made from milk such as cheese, yogurt, and ice cream are generally not fortified. Only a few foods naturally contain significant amounts of vitamin D, including fatty fish and fish oils. Cereals are often fortified with vitamin D.

    Exposure to sunlight is an important source of vitamin D. Ultraviolet (UV) rays from sunlight trigger vitamin D synthesis in the skin. In far southern or northern latitudes, the average amount of sunlight is insufficient to produce significant vitamin D synthesis in the skin in winter. Sunscreens with a sun protection factor (SPF) of 8 or greater will block UV rays that produce vitamin D, but it is still important to routinely use sunscreen whenever sun exposure is longer than 10 to 15 minutes. It is important for individuals with limited sun exposure to include good sources of vitamin D in their diets. Persons who have fat malabsorption may need extra vitamin D because it is a fat soluble vitamin.

    Persons over the age of 50 can have a higher risk of developing vitamin D deficiency because the ability of skin to convert vitamin D to its active form decreases as we age and the kidneys, which help convert vitamin D to its active form, are less functional with age.