Background: Echinococcal osteomyelitis is a rare localization of echinococcosis. Regarding the skeletal site, the spine is most commonly involved. Echinococcal osteomyelitis of the humerus is uncommon, even in endemic areas. In Thailand, only 28 cases of echinococcosis have been reported. Musculoskeletal involvement was identified in two of these cases. None involved the humerus.

Case Report: In the present report, the authors describe a rare case of indigenous echinococcal osteomyelitis of the humerus in an 18-year-old Thai woman from Ratchaburi province who presented with pathologic fracture.

Conclusion: This particular case does suggest that echinococcal osteomyelitis, despite its rarity, can be encountered in non-endemic areas including Thailand. Since its clinical and radiographic manifestations can mimic tumors and other inflammatory conditions, the disease might be overlooked. Histopathologic examination of the lesion is crucial for making diagnosis of echinococcal osteomyelitis.

Keywords: Echinococcal osteomyelitis, Osseous echinococcosis, Osseous hydatidosis, Hydatid disease of bone, Osteomyelitis