POEMS Syndrome Presentation with an Abscess within the Plasmacytoma-A Rare Case Report.

POEMS Syndrome is a rare cause of demyelinating and axonal mixed neuropathy. Plasmacytomas are usually seen in POEMS syndrome and can be osseous or extramedullary. Plasmacytomas presenting as an abscess has not been noted earlier. Our patient presented with localized hyperpigmented patch on the back and later developed progressive weakness in upper and lower limbs. Initially serum and urine protein electrophoresis were normal. The patient was thought to have Chronic Inflammatory Demyelinating Polyneuropathy and was treated accordingly without any improvement. Repeat serum protein electrophoresis showed monoclonal gammopathy. MRI of the back revealed an abscess in the paravertebral soft tissues reaching up to the skin. Needle biopsy was consistent with plasmacytoma. Later, he developed a purulent fungating lesion in the lower midback. Antibiotics were started and local resection was done followed by radiation. Pathology of the resected mass showed plasmacytoma extensively involving subcutaneous soft tissue and bone. The patient improved with the treatment. Cystic plasmacytomas and abscess within the plasmacytoma has not been reported earlier. Whether abscess formation is part of the disease spectrum due to infiltration of overlying tissue or is secondary to localized immunosuppression is unknown. Local treatment of a single plasmacytoma is useful in ameliorating systemic symptoms.