Mandibular mass as the presenting manifestation of IgM myeloma in a 22-year-old man.

We report here the youngest known IgM myeloma patient to have presented with a mandibular mass. A 22-year-old Chinese man sought medical attention due to a mass over his right mandible that had been growing progressively for 6 months. A solitary osteolytic lesion in the right mandible was identified radiologically. Incisional biopsy revealed the presence of plasma cells of monoclonal origin, as evidenced by the exclusively positive staining of the kappa light chain. The diagnosis of multiple myeloma with mandibular involvement was confirmed by bone marrow examination. Further tests, including immunoglobulin electrophoresis and assay of the serum levels of kappa and lambda light chains, demonstrated that his myeloma was of the IgM, kappa subtype. The patient achieved a nonsustained partial response to six courses of melphalan and prednisolone therapy and palliative radiotherapy.