Late onset hyperplastic callus formation in osteogenesis imperfecta type V simulating osteosarcoma—A case report

INTRODUCTION: We report a case of late onset hyperplastic callus formation (HPC) in the right femur in type V osteogenesis imperfecta (OI) mimicking the occurrence of a malignant osteosarcoma. PRESENTATION OF CASE: A 27-year-old female patient consulted us due to swelling in her right femur over 2–3 months without trauma. X-rays looked like an osteosarcoma, blood tests showed increased bone metabolism. A CT scan, a MRI and biopsy were performed, showing late onset HPC due to osteogenesis imperfecta type V. DISCUSSION: OI shows a heterogeneous disease pattern due to a variety of clinical and radiographic findings. HPC is a rare complication of OI type V. Differential diagnosis range from cortical or periosteal osteosarcoma, periostitis, myositis ossificans, subperiosteal hematoma secondary to trauma or osteomyelitis. CONCLUSION: Recognition of HPC as a form of this particular type of OI is important to avoid misdiagnosis like malignant transformation to osteosarcoma. A biopsy and advanced imaging modalities like CT, MRI and scintigraphy are recommended.