Atypical Bone Scintigraphy Findings in SAPHO Syndrome: A Case-Based Comparison With Typical Imaging Patterns.

SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, and osteitis) is a rare autoinflammatory disorder characterized by diverse skeletal and dermatologic manifestations. Bone scintigraphy plays a pivotal role in diagnosis, with the classic "bullhead" sign reflecting anterior chest wall involvement. Nevertheless, atypical scintigraphic patterns, particularly spinal involvement, can pose diagnostic challenges. We report 2 cases: one demonstrating typical tracer uptake in the manubrium and bilateral sternoclavicular joints, and another exhibiting predominant spinal osteitis. These cases illustrate the broad spectrum of scintigraphic presentations in SAPHO syndrome and underscore the complementary utility of SPECT/CT in delineating atypical lesions and facilitating accurate diagnosis.