Background: Langerhans cell histiocytosis (LCH), typically found in children, is a rare single or multisystem disorder with a wide range of clinical and radiological manifestations. Unusual presentations of LCH are occasionally encountered and it may be difficult to distinguish LCH from an infection or a benign or malignant tumor. Results: A 35-year-old female presented with pain in her back and left buttock, malaise, and weight loss, with a duration of several months. Her laboratory test results were within the normal ranges except for the levels of acute phase reactants, which were elevated. Magnetic resonance imaging and computed tomography revealed a unilateral destructive sacroiliac lesion, and multiple vertebral lesions with adjacent discal involvement and extensive soft tissue extensions. She was initially misdiagnosed with multifocal osteoarticular tuberculosis. An open biopsy and joint curettage was performed. Histopathological examination showed that she had LCH. Conclusion: To the best of our knowledge, this is the first case of LCH associated with a destructive unilateral sacroiliac lesion, discal involvement, and involvement of the adjacent vertebrae, in an adult patient; the LCH mimicked osteoarticular tuberculosis. Disease onset in adulthood is rare, and this can potentially delay diagnosis. Familiarity with the imaging features of unusual LCH manifestations is necessary to ensure accurate diagnosis and appropriate treatment.