NCMP-12. AN ATYPICAL CASE OF POEMS WITH MACROFOCAL MYELOMA

Abstract Polyneuropathy, organomegaly, endocrinopathy, M-protein, skin changes (POEMS) syndrome is a rare paraneoplastic syndrome secondary to an underlying plasma cell dyscrasia. Symptoms of peripheral neuropathy dominate the clinical picture and is postulated to be related to serum vascular endothelial growth factor (VEGF) mediated altered permeability of the blood nerve barrier. The classic presentation includes a solitary osteosclerotic plasmacytoma and an elevation of VEGF. In this case, we present a patient with neither of these features who met diagnostic criteria for POEMS though had predominantly osteolytic lesions and was diagnosed with macrofocal myeloma, a unique subset of multiple myeloma. Our patient is a young male who presented with progressive leg numbness/weakness and was found to have marked ankle weakness, diffuse areflexia and unilateral gynecomastia on examination. EMG showed a motor predominant demyelinating polyneuropathy. Labs showed a serum IgG lambda M protein, low estradiol and low testosterone. He had a normal serum VEGF level though the lab was drawn after treatment initiation. Bone biopsy of a dominant osteolytic lesion was consistent with a plasma cell neoplasm (light chain restricted). Of note, he had mild cauda equina nerve root and ventral conus enhancement initially concerning for leptomeningeal involvement however, two lumbar punctures were negative for malignant cells. Spinal enhancement has been reported in POEMS. The patient underwent chemotherapy, radiation therapy and autologous stem cell transplantation. We present a patient diagnosed with MFMM, a rare subset of multiple myeloma, comprising only 3% of all cases, along with POEMS, a rare paraneoplastic syndrome. Interestingly, as osteolytic lesions can be seen in POEMS alone though not predominantly so, it is possible the patient could have atypical POEMS without underlying multiple myeloma. POEMS may remain under-recognized when presentations or setting are atypical.