Solitary plasmacytoma presenting as peripheral neuropathy: a case report.

We report a 26 year old woman presenting with a chronic predominantly motor radiculoneuropathy. A biopsy proven solitary lytic plasmacytoma was detected in the left sixth rib. Serum immunoelectrophoresis revealed 'M' band (IgG, l light chain). Excision of the plasmacytoma resulted in gradual but steady recovery. We suggest that all patients with 'cryptogenic' polyneuropathy be investigated for this potentially treatable condition. A high index of suspicion assists the organization of appropriate diagnostic investigations.