[Cauda equina relapse after autologous stem cell transplantation in a patient with primary plasma cell leukemia]

We report a rare case showing involvement with the cauda equina after autologous peripheral blood stem cell transplantation for primary plasma cell leukemia (PCL). A 55-year-old man was diagnosed with PCL(IgA-k type, stage III)in November of 2006. He was treated with VAD chemotherapy consisting of vincristine, doxorubicin, and dexamethasone. After achieving hematological remission, he received tandem high-dose melphalan supported by autologous peripheral blood stem cell transplantation. Five months after his second transplant, he complained of lumbago and bilateral leg pain. M-protein and Bence-Jones protein were not detected in serum or urine. An axial magnetic resonance imaging study revealed enlargement of the cauda equina nerve roots on T-1 weighted image. A sagittal T-1 weighted gadolinium-enhanced imaging study showed hyperintensities along the cauda equina. Leptomeningeal enhancement was also seen below the level of Th6. A cytological examination of the cerebrospinal fluid (CSF) with May-Giemsa stain showed atypical plasma cells. Immunoelectrophoresis of the CSF revealed monoclonal IgA-k type protein. A diagnosis of central nervous system (CNS)relapse was made. The patient died of pneumonia two months after relapse. It should be kept in mind that CNS relapse can occur during hematological remission in patients with multiple myeloma including PCL.