Purpose or Case Report: Chronic non-infectious osteomyelitis (CNO) is an autoinflammatory disorder of unknown etiology that is characterized by sterile, painful, and destructive bone lesions and has its peak incidence in childhood. Its presentation can be highly variable, and when children present with solitary lesions having an indolent course, the clinical picture and imaging features at presentation can overlap with those of Ewing sarcoma (EWS), a rare, highly malignant, primary pediatric bone tumor with a poor prognosis. Osteomyelitis is a known imaging mimic of EWS, but CNO poses a particular problem because a lack of clinical markers usually indicative of infection can cause the disease to be mistaken for a malignancy at clinical workup as well as imaging. A misdiagnosis between these two diseases may have serious repercussions for treatment and clinical course with potentially devastating effects on patient outcomes.
Methods & Materials: We report a series of confirmed cases of patients with either CNO or EWS from our institution where the diagnosis was in doubt at presentation, and review in detail the clinical and multimodality imaging features of each case. An accompanying literature review provides a summary of existing work that has characterized the imaging features of CNO and EWS and has described some features that may differentiate EWS from osteomyelitis generally.
Results: We discuss the similar and dissimilar findings for each entity among our cases, with an aim to describing those features that may aid radiologists in differentiating unifocal CNO lesions from EWS. A potential pathway or guide that may help the interpreting radiologist reach a diagnosis more quickly and accurately is also proposed.
Conclusions: Both CNO and EWS need to be considered in the differential diagnosis for a solitary bone lesion with aggressive features in a child. Enabling pediatric radiologists to have a better understanding of the overlapping and contrasting characteristics of CNO and EWS will reduce the risk of misdiagnosis between the two.