Primary Histiocytic Sarcoma (HS) is an aggressive rare neoplasm of the lymphohematopoietic stem cells especially involving the central nervous system. This is an unusual case presentation of primary CNS HS and highlights the rapid clinical progression of disease and work-up leading to a diagnosis.

This case presentation has qualities supporting further discussion regarding its potential for misdiagnosis and highlights the rapid progression of the disease process despite relatively benign symptoms at onset. Primary HS of the CNS should be considered as a possible cause of sudden onset of lower back pain progressing rapidly to weakness of the lower extremities bilaterally in addition to multiple cranial nerve impairments.