Monostotic Paget's disease of the femur: A diagnostic challenge and an overlooked risk

Abstract Background Although radiological diagnosis of Paget's disease of bone (PD) is usually straightforward, monostotic cases may potentially raise specific problems which lead to performing invasive procedures. Therefore, the purpose of this study is to ascertain whether or not monostotic femoral Paget's disease (MFPD) presentation poses particular diagnostic difficulties which prompt excessive use of excisional biopsies. Methods We retrospectively reviewed the medical records of 24 MFPD patients identified from a series of 412 patients; their clinical features were compared with those of the remaining 164 monostotic cases and the radiological images were systematically assessed. Results When compared with the remaining monostotic cases, MFPD patients were more prone to having normal alkaline phosphatase levels (31.8% vs. 16.4%; 0.08) and a significantly higher percentage of patients have PD symptoms (75% vs. 51%; 0.02) and complain of bone pain (73.9% vs. 40.8%; 0.003). Six (25%) MFPD patients evidenced a fracture over the pagetic lesion. This incidence is higher than that of the monostotic cases of other locations (8.4%; p = 0.02). The existence of PD lesion was not recognised initially in 10 cases and an excisional bone biopsy was performed in 7 (29%). One patient subsequently experienced a fracture through the biopsy site and another two experienced worsening of their previous bone pain. Conclusion The femur is a relatively common monostotic PD location which often causes diagnostic confusion, prompting a bone biopsy in many cases. Careful assessment of this lesion by X-ray examination may help attain an early appropriate diagnosis and avoidance of unnecessary surgical morbidity.