Polyarthritis Associated with Monoclonal Gammopathy - an Unusual Case with Plasmacytoma

Polyarthritis is an unusual way of presentation of plasmacell dyscrasias. It has occasionally been described in relation with a monoclonal gammopathy of uncertain significance (MGUS) and in a few cases associated with a multiple myeloma (MM). We present a singular case in which the arthropathy took place in a patient with a monoclonal immunoglobulin producer solitary osseous plasmacytoma. A 46-year-old man developed, during a period of 3 months, a migratory polyarthritis with a severe disability, involving knees, shoulders, wrists, and metacarpophalangeal joints of both hands with a poor response to nonsteroidal anti-inflammatory drugs. The episodes were not activity related and were brief and recurrent, involving 2 or 3 joints in the same time in an asymmetric pattern. Pain, stiffness, and restriction of movement were present with mild swelling and erythema. Sometimes, the knees were involved with scanty synovial effusion. We did not tap any joint. In addition, he had low-grade fever, asthenia, and weight loss. After that, he started complaining of pain and swelling in the left anterior chest wall. At his admission in the hospital, a IgG monoclonal gammopathy of 0.35 g/dL, an erythrocyte sedimentation rate of 50 mm/h, and normocytic anemia (hemoglobin level 10.2 g/dL) were observed, but C-reactive protein and creatinine levels, the calcium, plasma IgA and IgM levels, the urinary Bence Jones protein, rheumatoid factor, and the remaining autoimmunity and serological parameters were all within normal limits. Microbiological investigations were negative. Skeletal radiographs were performed, and a lytic lesion was found in the front arch of the 7th left rib. There were no other skeletal or joint erosive lesions found. A computed tomography scan showed a slight soft tissue component around the lytic lesion. A needle aspiration of the rib was made without any significant results, and the bone marrow biopsy showed just 4% plasma cells. The 7th rib was excised, and the histologic examination revealed a plasmacytoma. After that, the symptoms and the monoclonal peak disappeared, with the patient remaining asymptomatic in the next 2 years of follow-up. Bone pain is an usual form of presentation of MM. Arthritis in the amyloidosis and its association to MM is well known, but arthritis associated to a monoclonal gammopathy is less frequently seen: We have found just 20 cases of MGUS-associated arthritis in the literature, and all the experience observed in relation with plasma-cell dyscrasias is associated to MM. We have not seen any plasmacytomaassociated arthritis described in our review. The solitary osseous plasmacytoma usually presents with pain at the site of the bone lesion. The most affected region is the axial skeleton, and the M protein is present in 4% to 10% of the cases. The arthritis associated to a monoclonal gammopathy has been described as seronegative, peripheral, and polyarticular. It can sometimes involve big joints and joints that are infrequently affected in rheumatoid arthritis (RA) and can produce erosions. It can occasionally behave as a gout-like arthritis presenting oligoarticular exacerbations. Fever and a constitutional syndrome may be present, and laboratory investigations may show anemia and elevation of erythrocyte sedimentation rate, but C-reactive protein is usually within normal limits. Synovial fluid, when analyzed, is inflammatory. Both sexes are equally affected. The most common monoclonal component of the described cases has been IgG , but occasionally, as in the case we show in here, the M protein was composed by IgG . The arthritis may appear simultaneously with the monoclonal peak or it may develop after this. The differential diagnosis should include RA, psoriatic arthritis, and MM-associated amyloid erosive arthritis. The risk for developing plasma-cell dyscrasia is increased in patients with RA, but the arthritis in these cases is clinically typical, seropositive, and it is usually present years before the onset of the gammopathy. The pathogenesis of these inflammatory problems MGUS-associated arthritis is not clear, but crystallizing paraproteins have been demonstrated in synovial fluid and tissue, and they appear to be initiating the inflammatory response that will lead to the arthropathy in some cases. The response to usual treatments used for chronic arthritis is poor, but the extirpation of the plasmacytoma will be followed, as in the case we present, by the simultaneous and maintained disappearance of the M protein and the arthritis. In our opinion, plasma cell dyscraFrom the Services of *Internal Medicine, and †Hematology, Hospital Galdakao, Galdakao, Bizkaia, Spain. Reprints: Dr. Juan Carlos Urkijo, Service of Internal Medicine, Hospital Galdakao, B° Labeaga s. n., 48960, Galdakao, Bizkaia, Spain. E-mail: medin01@hgda.osakidetza.net. Copyright © 2007 by Lippincott Williams & Wilkins ISSN: 1076-1608/07/1304-0240 DOI: 10.1097/RHU.0b013e318133dbce