Antacid-induced osteomalacia: a case report with a histomorphometric analysis

The case of a 75-year-old woman with severe osteomalacia secondary to ingestion of large amounts of an aluminum-containing antacid is reported. Biochemical analysis revealed signs of phosphate malabsorption and increased levels of bone markers (S-alkaline phosphatase and U-hydroxyproline). A 99mTc-bone scan revealed multiple areas of increased uptake. The patient was normocalcaemic, with normal serum levels of intact parathyroid hormone and 25-hydroxyvitamin D. Serum 1,25-dihydroxyvitamin D was high normal. A transiliac bone biopsy from the patient showed severe osteomalacia. Symptoms, biochemical parameters, bone scan and bone morphology were all normalized 1 year after stoppage of antacid ingestion and treatment with vitamin D2. calcium phosphate and sodium fluoride because of severe osteopeni. The characteristics of this condition and the role of phosphate depletion and aluminum in the pathogenesis of bone lesions are discussed.