Diffuse midline glioma in Ollier disease: A case report and a brief review of the literature.

Ollier disease is a rare condition presenting with enchondromas in an irregular distribution within the medullary cavity of bones. The disease is well known for sarcomatous transformation to chondrosarcomas. It also increases the risk of other malignancies like leukemia, ovarian tumors, and glial tumors. Central nervous system malignancies associated with Ollier disease are thought to arise by somatic IDH mosaicism with their atypical features of distribution, multifocality, and age of onset. We present a case with imaging consistent with diffuse midline glioma in a patient with Ollier disease. We conclude with a brief review of the literature on Ollier Disease with a focus on central nervous system malignancies, tumorigenesis and pathophysiology.