A retrospective study of bone scintigraphy in the follow-up of patients with synovitis, acne, pustulosis, hyperostosis, and osteitis syndrome: is it useful to repeat bone scintigraphy for disease assessment?

Objectives To investigate the value of repeated bone scintigraphy in the follow-up of patients with synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome and to characterize the changing pattern of osteoarticular lesions revealed by bone scintigraphy. Method Twenty-four patients with SAPHO syndrome who had repetitively undergone bone scintigraphy and tests of inflammatory markers (erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP)) were included in this retrospective study. The change in accumulation number was recorded as the difference in the number of accumulation sites between consecutive bone scintigraphy. The visual analog scale (VAS) for pain and medications prescribed were also reviewed. The relationships of the change in accumulation number with medication prescribed and change in ESR or CRP were analyzed. Results Twenty-four and 23 patients had follow-up tests of ESR and CRP, from which 30 and 28 follow-up data were obtained, containing the corresponding changes in ESR and CRP, respectively. A decrease in total accumulation number observed by bone scintigraphy was rarely observed, while decreases in ESR, CRP, and VAS were predominant. The accumulation number had significantly increased over time (follow-up with ESR: r = 0.389, p = 0.034; follow-up with CRP: r = 0.438, p = 0.020), in accordance with an “imprinting” pattern, while the inflammatory markers and VAS for pain predominantly decreased. There was no significant association between the change in accumulation number (local/total) and the change in ESR or CRP values ( p > 0.05) or medications used for SAPHO ( p > 0.05). Conclusions This retrospective cohort study of 24 SAPHO patients demonstrated an “imprinting” pattern on bone scintigraphy, without a correlation to the decrease in inflammatory markers, patient disease assessment, or treatment type. Thus, repeated bone scintigraphy did not contribute an additional clinical value for the follow-up of patients with SAPHO. Key Points • In a cohort of 24 SAPHO patients, repeated bone scintigraphy revealed a continuous increase in tracer accumulation number, indicating an “imprinting” pattern. • The change in tracer accumulation number, defined as the difference in the number of accumulation sites between consecutive bone scintigraphy measurements, was inconsistent with the change in ESR, CRP, or VAS for pain. • The medications prescribed for SAPHO did not seem to contribute to a decrease in accumulation n