Stress fractures of the lower extremity in methotrexate-induced osteopathy: A case report.

We report a case of metachronous stress fractures in the bilateral lower extremities associated with methotrexate (MTX)-induced osteopathy in a 61-year-old woman. She had been treated with low-dose MTX for 4 years for rheumatoid arthritis (RA) and acute lymphoblastic leukemia (ALL). She presented with a 2-month history of right ankle pain and swelling without trauma. Magnetic resonance imaging revealed stress fractures in the distal tibial metaphysis, calcaneus, and talus. The tibial lesion appeared meander-shaped along the growth plates, hypointense on T1-weighted images, with surrounding bone marrow edema hyperintense on fat-suppressed T2-weighted images. The patient received nonweight bearing therapy while continuing low-dose MTX for maintenance of remission in ALL. Twelve months later, pain developed in the contralateral ankle, and MRI demonstrated a stress fracture in the left distal tibial metaphysis. We diagnosed metachronous stress fractures due to MTX-induced osteopathy. Although rare, clinicians and radiologists should be aware of the potential for stress fractures in the lower extremities, particularly the distal tibial metaphysis, in patients receiving low-dose MTX who present with ankle pain.