Introduction: Chronic primary osteomyelitis (CPO) is a rare disease, defined as a chronic inflammatory process involving cortical and medullary bone. In the maxillofacial region, it mainly affects the mandible, with a predilection for females in a wide age range, with unknown etiology or defined treatment protocol. Objective: The objective of this article is to report a case of the rare disease Chronic Primary Osteomyelitis, focusing on its clinical, radiographic, and histopathological characteristics, and to discuss the nomenclature for differential diagnosis while comparing with other osteomyelitis. Case Report: MLP patient, 53 years old, female, leukoderma, was admitted at the Maxillofacial Surgery and Traumatology Service of the University Hospital of USP referred from another service and reported of severe pain and swelling in the face for approximately 1 .5 year. On clinical examination, he presented edema 1+/4+ in the lower third of the right hemiface, sensitive to palpation, trismus, lower lip paresthesia, no evidence of infectious odontogenic focus, increased volume or intraoral secretion. The patient was submitted to an incisional biopsy, computed tomography and scintigraphy, which showed an sclerotic pattern and increased uptake in the mandible, respectively. After months of antibiotic therapy with no results, the patient was initially submitted to 20mg of Prednisone with regression up to 5mg and two doses of 60mg of Pamidronate which resulted in remission of pain, edema and trismus. Until the publication of this article, the patient had no recurrence of the symptoms, totalizing 6 years of follow up. Conclusion: CPO is a rare and challenging diagnosis disease. Prednisone was effective to edema and trismus decreasement and Pamidronate for pain control, however more studies are necessary to determine a definitive treatment for this condition.