Plasma cell leukemia (PCL) is a rare (1-4% of plasma cell malignancies) and aggressive plasma cell dyscrasia which even more rarely invades the central nervous system (CNS). The neurological manifestations can include cerebral, cranial nerve, spinal cord, and nerve root infiltration. Prognosis is poor and survival is about 2-6 months even with aggressive treatment. We report a patient with PCL whose relapse presented with CNS involvement.

 A 43-year-old man with history of PCL status post haploidentical stem cell transplant presented with a one week history of progressive left sided weakness. Examination showed left sided weakness with 4/5 muscle strength on MRC scale. His left upper extremity strength and reflexes in the left arm decreased over the next day.  There were no cranial nerve deficits or sensory findings on exam.

MRI of the brain showed a new small parenchymal enhancement within the left superior temporal gyrus. MRI spine showed extraosseous expansion into the epidural space at T12 without cord compression. MRI brain and spine did not explain his neurological findings. Lumbar puncture showed protein 72mg/dL, glucose 117mg/dL (serum glucose 223mg/dL), and nucleated cell count of 188/mm3 (97% of which were atypical cells). Immunophenotypic analysis detected approximately 80% monoclonal plasma cells expressing bright CD38, CD56 (small subset), dim CD138 and cytoplasmic lambda. Together with review of the Wright stained cytology preparation this was consistent with CNS plasma cell leukemia.

The clinical presentation suggested rapidly progressing infiltration of left upper extremity nerve roots. CSF demonstrated leukemic meningitis. He was treated with intrathecal chemotherapy with Methotrexate which showed cytologic improvement.