A Case of Lytic Bone Lesions and Unexpected Laboratory Findings: Navigating Diagnostic Uncertainty

We present a case of a 66-year-old male patient who presented with progressive generalized weakness and was found to have diffuse lytic lesions involving the calvarium and entire spine. Diffuse lytic bone lesions identified on imaging prompted an extensive evaluation for malignant and non-malignant etiologies. In cases with atypical laboratory findings and negative bone marrow biopsy, diagnosis and management can be complicated. Imaging was initially highly suspicious of malignancy, but further investigation revealed abnormal serum free light chain levels. Additionally, a negative serum and urine protein electrophoresis and bone biopsy revealed no evidence of malignancy or plasma cell dyscrasia. This unique case highlights the diagnostic difficulty and importance of interpretation and lateral surveillance in patients with suspected plasma cell dyscrasia.