Osteomalacia due to vitamin D depletion: a neglected consequence of intestinal malabsorption

Osteomalacia due to vitamin D depletion is believed to be rare in the United States because of the routine fortification of milk and other dairy products with vitamin D. We present a series of patients with histologically verified osteomalacia due to vitamin D depletion to emphasize the need for more careful and systematic surveillance of patients at risk of this metabolic bone disease.

Between 1989 and 1994, 17 patients with osteomalacia due to vitamin D depletion were seen in the Bone and Mineral Division of Henry Ford Health System, Detroit. All patients had a transiliac bone biopsy after in vivo double tetracycline labeling. Biochemical indexes of vitamin D nutritional status, parathyroid function, markers of bone turnover, and bone mineral density were assessed at the time of bone biopsy. The duration of symptoms, the lag between the cause of vitamin D depletion and the development of symptoms, and the radiologic findings were recorded.

Osteomalacia was suspected by the referring physician in only 4 of the 17 patients, although a gastrointestinal disorder that can lead to vitamin D depletion was present in every patient. Thirteen of the patients had sustained at least one osteoporotic fracture (wrist, spine, or hip), and most had low appendicular and axial bone mineral density. All patients had one or more biochemical abnormalities consistent with vitamin D depletion. In 4 patients, a progressive rise in the serum alkaline phosphatase level was recorded but was not investigated until the patient presented with bone pain, muscle weakness, or fracture.

Osteomalacia due to vitamin D depletion appears not to be suspected or diagnosed promptly in susceptible patients, perhaps because their physicians were not sufficiently aware of this condition.