Bilateral Stress Fractures of the Lower Extremity in Methotrexate Osteopathy

A 55-year-old female patient with seronegative rheumatoid arthritis (RA) was admitted as an inpatient due to atraumatic, treatment-refractory, and immobilizing bilateral lower extremity pain. Treatment with methotrexate (MTX) (20 mg s.c. weekly) and prednisolone (most recently, 5 mg p.o. daily) had been ongoing since the initial RA diagnosis 17 years previously. There were no clinical signs of RA activity at the time of admission. Magnetic resonance imaging (MRI) investigations of the lower extremity revealed bilateral stress fractures in the region of the distal femur as well as the proximal and distal tibia (figure). DXA bone densitometry revealed severe osteoporosis (T-score –4.6). Based on a consideration of all findings, the diagnosis of MTX osteopathy was made. MTX osteopathy is a rare complication of MTX therapy, which is characterized by a triad of immobilizing pain, atraumatic stress fractures of the lower extremity, and osteoporosis. The morphological picture on MRI of meander-shaped stress fractures along the former epiphyseal plate is considered pathognomonic. The only successful treatment option comprises discontinuation of MTX medication combined with highly potent specific osteoporosis treatment (in this case, denosumab + teriparatide).

Figure.

MRI investigations of the lower extremity

a) Knee joint, b) ankle joint (coronal T2 weighting), with the finding of bilateral stress fractures in the region of the distal femur as well as the proximal and distal tibia

(Performed by: Dr. med. T. Abel, Radiologie Klinikum Bad Bramstedt, Germany).

Translated from the original German by Christine Rye.