Chronic intoxication by ethane-1-hydroxy-1,1-diphosphonate (EHDP) in a child with myositis ossificans progressiva

A child with myositis ossificans progressiva was treated for 8 years with ethane-1-hydroxy-1,1-diphosphonate (EHDP) 30-40 mg/kg per day. Latterly he complained of severe, progressive bone and joint pain which made standing and walking almost impossible. A radiographic skeletal survey showed diffuse ricket-like lesions. Withdrawal of EHDP therapy produced substantial improvement in his general condition as well as in the radiographic appearance of the bones. Multiple exostoses were observed in this case and, particularly those around the knees, presented a peculiar morphology. This supports the theory that exostoses originate from a defect of metaphyseal modelling.