MON-812 - Paget'S Disease of Bone with Normal Alkaline Phosphate Mimicking Metastatic Disease

Introduction:
Paget’s disease of bone can be asymptomatic or present as bone pain. Elevated alkaline phosphatase is commonly present as a result of bone remodeling, however a normal level of alkaline phosphatase can be seen as in this patient. Although MRI is often used to assess complications from Paget’s disease of the bone such as malignancy, this case highlights how this patient’s findings on MRI lead to additional work-up which landed the diagnosis and patient was appropriately managed.

Case report:
52-year-old female presented with left-sided back pain. Chemistry panel showed a normal alkaline phosphatase level at 113 U/L, and normal calcium. A CT renal study showed incidental findings of T10 and T11 vertebral bodies with moth-eaten appearance concerning for malignancy. MRI of thoracic spine exhibited patchy faint areas of decreased T1 and T2 in thoracic spine without evidence of enhancement for which nonspecific sclerotic changes or benign bone marrow replacement was suggested. Additionally, had benign appearing hemangiomas in T10 and T12 vertebral bodies. Bone scan showed multiple foci of increased activity within the thoracic spine and diffusely increased activity in the right femoral head, neck, and greater trochanter, and at the left talus area, which worried about metastatic disease.
A bone specific alkaline phosphatase level was normal at 18.4 ug/L, C-telopeptide was normal at 482 pg/mL, and N-telopeptide/creatinine ratio resulted above normal at 119 nM BCE/mM Cr which favored Paget’s disease of the bone.
A T10 vertebral body biopsy revealed sclerotic bone with pagetoid changes, hypercellular trilineage maturing hematopoiesis with no increase in blasts, and was negative for metastatic carcinoma and plasma cell neoplasm.
Treatment with a single dose of intravenous zoledronic acid 5 mg, led to symptomatic improvement and a decline in C-telopeptide to 92 pg/mL and N-telopeptide/creatinine ratio to 21 nM BCE/mM Cr.


Discussion:
This case highlights the diagnostic complexity of Paget’s disease of bone in the presence of normal alkaline phosphatase levels and nonspecific MRI findings. Comprehensive evaluation incorporating advanced imaging, bone turnover markers, and histopathology is essential to establish the diagnosis and guide appropriate management.

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