A Case of Nonsecretory Multiple Myeloma with Atypical Imaging Features
A 45-year-old man was admitted to our hospital because of a one month history of fatigue and severe back pain for two days prior to presentation. There were no specific findings on physical examination. Results of routine laboratory tests showed a mild anemia (hemoglobin, 11.4 g/dL; normal range, 14~18 g/dL). A corrected reticulocyte count was slightly decreased (0.4%; normal range, 0.5~2.5%), suggesting impaired marrow synthesis of erythrocytes. The albumin to globulin ratio (A/G ratio) was normal (A/G ratio, 1.43; albumin, 3.0 g/dL; globulin, 2.1 g/dL). The serum C-reactive protein was markedly increased (151.0 mg/dL; normal range, 0.0~0.5 mg/dL). The serum creatine and total calcium levels were normal. The serum and urine protein electrophoreses, and immunofixation electrophoreses to detect protein more than 20 mg/dL, were repeatedly negative. The level of β2 microglobulin was also normal.\nThere was no evidence of lytic bone lesions on plain radiograph. Contrast enhanced chest CT obtained on admission showed multiple, well-defined, osteolytic lesions at the 8th and 11th thoracic vertebrae (). MRI showed the lesions to be hypointense on T1-weighted image (500/15) () and heterogeneously hyperintense on T2-weighted image (1800/90) (). Although these were very small foci of enhancement, at the lesions of 8th and 11th thoracic vertebrae, most of the lesions were poorly enhanced on T1-weighted image () after intravenous administration of gadopentetate dimeglumine (Magnevist; Schering, Seoul, Korea). The radiological differential diagnosis was multiple myeloma, metastasis and tuberculosis. Two days after the MRI, a CT-guided gun biopsy was performed on the poorly enhancing portion of the lesion at the 8th thoracic vertebra. The biopsy showed a coagulation necrosis within a population of uniform, monotonous cells (). However, the definite diagnosis was not made at that time because the pathologist considered this finding to be nonspecific. Polymerase chain reaction (PCR) was performed with part of biopsy specimen obtained from the 8th thoracic vertebra using an M tuberculosis kit (Amplicor; Roche Diagnostic Systems, Somerville, NJ), which amplified part of the 16S rRNA gene. The result of the PCR was positive for M tuberculosis. Although pathologic confirmation of tuberculous granuloma with caseation necrosis was not proven, a presumptive diagnosis of tuberculous spondylitis was made. Combination chemotherapy with isoniazid (Yuhan-zid; Yuhan, Seoul, Korea), rifampin (Yuhan), etambutol (myambutol; Yuhan), and pyrazinamide (Yuhan) was started. Twenty-five days after the biopsy, the patient complained of more severe and constant back pain. A thoracolumbar roentgenogram showed compression fractures of the 8th and 11th thoracic vertebral bodies. Follow-up CT examination showed a new osteolytic lesion (), with a well-defined outer margin and cortical disruption, at the junction of the spinous process and the lamina of the 12th thoracic vertebra; this lesion showed strong enhancement after intravenous administration of contrast media. On a retrospective review of the previous CT studies, this lesion () had been overlooked. The next day, a CT guided gun biopsy of the lesion at the 12th thoracic vertebra was performed. Histological examination of the biopsy tissue showed a proliferation of plasma cells (). There was a strong positive reaction for the lambda light chain (). On the basis of these findings, we considered that the lesion at the 8th thoracic vertebra was also a plasma cell lesion with coagulation necrosis. The tissue from a bone marrow biopsy of the right posterior iliac bone showed 40% plasmacytosis. A diagnosis of a stage I nonsecretory myeloma was made. Combination chemotherapy with intravenous adriamycin (Il-dong Pharmaceuticals, Seoul, Korea), vincristine (Boryung Pharmaceuticals, Seoul, Korea), and dexamethasone (Il-sung Pharmaceuticals, Seoul, Korea) was started in a dose of 13.5 mg, 0.4 mg and 400 mg per day for four days, respectively.