PSAT196 Monostotic Paget's disease of the bone involving the calcaneus

INTRODUCTION: Paget's disease of bone (PDB) is a chronic bone disorder that is fairly common in older age. It is characterized by an initial increase in osteoclastic activity followed by excessive osteoblastic activity with disorganized bone architecture. PDB may involve any bone and may be monostotic or polyostotic. Herein, we report the rare occurrence of monostotic Paget's involving the calcaneus. CASE DESCRIPTION: A 71-year-old white male with PMH of prostate cancer status post radical prostatectomy presented with acute onset severe left heel and ankle pain. Pain was localized to the retrocalcaneal area and heel pad limiting his physical activity. He denied recent trauma. Physical exam was significant for swelling and tenderness of the left heel. Left foot X-rays showed a slightly enlarged calcaneus with very coarse trabeculae consistent with PDB. A total body bone scan done previously because of the prostate cancer showed intense uptake in the left calcaneus but no significant uptake elsewhere. Laboratory workup showed an elevated total serum alkaline phosphatase of 164 U/L (40-129 U/L) and bone specific alkaline phosphatase 65 ug/L (0.0-20 ug/L). He was treated with a single infusion of Zoledronic acid with good clinical response evidenced by improvement in pain and swelling as well as a significant decrease in bone specific alkaline phosphatase to 10 ug/L six months post-infusion. DISCUSSION: Monostotic PDB only represents about 20% of PDB cases. The pelvis is the most common location followed by the femur as described by Bachiller-Corral et al (Bone, 2013). In our review of the English literature, we found only nine cases of monostotic PDB involving the calcaneus. The mean age of presentation was 60 years old and most of the cases presented as chronic heel pain not responding to conservative pain alleviating measures. Conventional radiography showed the characteristic features of PDB but the changes observed were difficult to differentiate from that of a malignant process. That led to further imaging in most cases by either CT, MRI scan or SPECT scan. Three out of nine patients were reported to receive bisphosphonate therapy with successful remission with a long duration of disease suppression. Good response to therapy highlights the importance of proper diagnosis. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.