Table 1_Case Report: SAPHO syndrome mimicking osseous relapse after haploidentical allogeneic hematopoietic stem cell transplantation for acute myeloid leukemia.docx

Computed tomography and technetium-99 m methylene diphosphonate bone scintigraphy with single-photon emission computed tomography/computed tomography demonstrated lesions involving the sternum, bilateral clavicles, and T6–T9 costovertebral joints. Computed tomography-guided sternal biopsy showed collagenized fibrous tissue with myxoid change, focal chondroid differentiation, a small amount of newly formed bone, and mild inflammatory-cell infiltration, without morphologic evidence of leukemic involvement.

The combination of severe acne and osteitis in a characteristic distribution, after clinical evaluation for malignancy and infection, supported a diagnosis of SAPHO syndrome. Serum interleukin-6 elevation and altered peripheral immune-cell subsets were considered exploratory single-time-point observations. Symptoms improved after methylprednisolone followed by celecoxib, methotrexate, and dermatologic treatment.</p>Conclusion<p>SAPHO syndrome should be considered when post-transplant bone lesions coexist with compatible skin manifestations.

Multimodal imaging and targeted biopsy helped avoid inappropriate treatment for presumed AML relapse. The observed immune abnormalities are hypothesis-generating and do not establish a causal relationship between allo-HSCT and SAPHO syndrome.</p>