[Solitary costal plasmacytoma: a rare cause of subacute demyelinating polyradiculoneuropathy].

INTRODUCTION: The solitary plasmacytoma (SP) is a non-frequent, localized variant of multiple myeloma with a single bone lesion and earlier appearance. Polyradiculoneuropathy is the most frequent neurological manifestation. We report the case of a young male who developed a subacute demyelinating polyradiculoneuropathy as the initial symptomatology of a costal SP, which constitutes an extremely infrequent association, given age and site of the lesion. CASE REPORT: A 32-year old, previously healthy, man presented with a one month history of progressive symmetrical paraparesis and paresthesias in feet. The neurological examination revealed 4/5 paraparesis, global arreflexia and hypopalesthesia in legs. Cerebrospinal fluid examination revealed elevated proteins (83 mg/dl) with normal cell count and glucose content. Investigations showed high levels of beta(2)-microglobulin (3 mg/l), and a monoclonal IgG lambda gammapathy. The chest X-ray and thoracic CT revealed an osteolytic lesion in the left third rib. Nerve conduction studies showed sensitive and motor polyneuropathy with secondary axonal degeneration. Bone marrow biopsy was normal. Second and third left ribs were excised, revealing a pathologic diagnosis of plasmacytoma. The patient became asymptomatic after corticosteriod administration lesion excision and local radiotherapy. Conclusions. Subacute demyelinating polyradiculoneuropathy can be due to multiple causes. SP can be one of its etiologies and occur at infrequent ages and localizations.