Muscle weakness as presenting symptom of osteogenesis imperfecta.

A young boy presented with severe muscle weakness of his legs at the age of 2 years. Muscle morphology and computer tomography imaging findings were compatible with a metabolic myopathy. Additional investigation showed an osteopenic skeleton and signs of healing fractures. A skin biopsy showed an abnormal electrophoresis pattern of collagen, consistent with a variant of osteogenesis imperfecta. The patient improved with intravenous treatment with pamidronate.