Osteomalacia with bone marrow fibrosis due to severe vitamin D deficiency after a gastrointestinal bypass operation for severe obesity.

OBJECTIVE: To present 5 cases of bone biopsy-proven osteomalacia with marrow fibrosis (in 3 cases) after gastric bypass operation, review the relevant literature, and offer preventive strategies.
METHODS: We summarize the clinical presentation, pertinent biochemical and radiologic data, and bone histomorphometric findings in 5 patients, encountered during a period of 17 years, in whom severe vitamin D deficiency developed after a gastrointestinal bypass surgical procedure for morbid obesity.
RESULTS: Five patients (39 to 60 years of age) were seen for evaluation of metabolic bone disease not responding to "usual" therapy after a gastric bypass surgical procedure. All had generalized bone pain and tenderness, muscle weakness, stooping posture, difficulty walking, and waddling gait due to severe proximal muscle weakness for a period of 2 to 5 years. Diagnoses before the referral varied from arthritis and gout to vitamin D deficiency and osteoporosis despite highly suggestive biochemical or radiologic findings (or both) of osteomalacia in each patient, which was confirmed by bone biopsy. After therapy with pharmacologic doses of ergocalciferol (100,000 IU daily) and calcium carbonate (1 to 2.5 g daily), considerable improvements occurred in clinical symptoms and functional status, biochemical indices, bone mineral density, and bone histomorphometric features.
CONCLUSION: Gastric bypass operations predispose patients to severe vitamin D deficiency and osteomalacia in the absence of pharmacologic doses of vitamin D therapy. In general, the current recommendations are grossly inadequate in this high-risk population, and the clinical presentation is both nonspecific and often misleading. Prospective long-term studies are needed to determine the appropriate vitamin D dose required to prevent osteomalacia in such patients.