ANTIBODIES TO Sm AND RNP

Transcription

1 848 ANTIBODIES TO Sm AND RNP Prognosticators of Disease Involvement ELLEN FIELD MUNVES and PETER H. SCHUR The charts of 190 consecutive patients found to have antibodies to Sm, ribonuclebprotein (RNP), or both were examined to determine these antibodies possible associations *th certain clinical conditions as well as their diagnostic specificities. Patients with anti- Sm were more likely to have renal disease and antibodies to double-stranded DNA, single-stranded DNA, and nuclear protein than were patients with anti-rnp. No clinical associations were found for anti-rnp. Although most of the patients with antibodies to Sm, RNP, or both had systemic lupus erythematosus, some had other diagnoses, including cutaneous lupus, drug-induced lupus, rheumatoid arthritis, juvenile arthritis, mixed connective tissue disease, Raynaud s disease, progressive systemic sclerosis, miscellaneous rheumatic and nonrheumatic diseases, and undifferentiated connective tissue disease syndromes. These findings suggest that these antibodies mdy be associated with some diseases, but are not disease-specific. Rheumatic diseases are frequently associated with the presence of certain autoantibodies. When two of these antibodies are present, i.e., anti-sm and antiribonucleoprotein (anti-rnp), specificity for the dis- From the Division of Rheumatology and Immunology. Brigham and Women s Hospital, Harvard Medical School, Boston, Massachusetts. Supported by NIH grants AM11414 and AM The Lupus Foundation of America, The Arthritis Foundation, and the New England Peabody Home Foundation. Ellen Field Munves, MD: PHS Postdoctoral Trainee; Peter H. Schur. MD: Professor of Medicine. Address reprint requests to Peter H. Schur, MD. Brigham and Women s hospital, 75 Francis Street, Boston, MA Submitted for publication June 28, 1982; accepted in revised form February 1, ease is suggested. Antibodies to Sm, a ribonucleaseresistant nuclear RNA protein (I), have been thought to be diagnostic for systemic lupus erythematosus (SLE), while antibodies to the ribonuclease-sensitive nuclear ribonucleoprotein RNP have been associated with mixed connective tissue disease (MCTD) (2-12). In the past decade, a number of investigators have attempted to define the clinical and diagnostic significance of these antibodies by examining their frequency in patients known to have rheumatic disease. The purpose of the present study was to determine whether the presence of these antibodies could predict the likelihood of any particular clinical characteristic or diagnosis. After examining all consecutive patients who happened to have these antibodies, ii-respective of diagnosis, we found that patients with anti- Sm were more likely to have renal disease than were those with anti-rnp but that, in contrast, anti-rnp had no unique clinical features. While most patients with anti-sm and/or anti-rnp had SLE, these antibodies were also found in patients with other rheumatic diseases, suggesting that these antibodies may show some degree of disease association, but not disease specificity. PATIENTS AND METHODS At the Brigham and Women s Hospital, 6,048 serum samples were sent to the Clinical Immunology Laboratory between November 1979 and October 1981, to be tested for antinuclear antibodies (ANA). Traditionally, most patients seen in the large Rheumatic Disease Division, as well as many patients in the other services, undergo ANA testing when they have vague complaints related to rheumatic disease or when lupus is suspected. Of the 6,048 ANA tests, 1,1 IS were positive, i.e., the titer was 1 : 10 or greater. All the serum samples were automatically screened for antibodies to Arthritis and Rheumatism, Vol. 26, No. 7 (July 1983)

2 ANTIBODIES TO Sm AND RNP 849 Table 1. Clinical features in 150 patients with antibodies to Sm andor ribonucleoprotein (RNP) Anti-Sm AntiSrn Anti-RNP and anti- (%) (rc) RNP (%I Signs and symptoms (42 patients) (76 patients) (32 patients) Arthritis Arthralgias Rashes Discoid lupus Alopecia Photosensitivity Mouth ulcers Pleuropericarditis Central nervous system manifestations Weight loss Fatigue Fever Raynaud s Esophageal Pulmonary Myalgidmyositis Sm and RNP. Of these, 150 patients were found to have antibodies to Sm, RNP, or both. These patients were selected for further study. The patients charts were then reviewed to assess the clinical and laboratory features listed in Tables 1 and 2. These included central nervous system (CNS) signs and symptoms (disturbances in mental function, motor disorders, neuropathy, seizures), esophageal signs and symptoms (dysphagia or hypomotility), pulmonary manifestations (restrictive disease, decreased diffusing capacity), and myalgias and/or myositis (elevated creatinine phosphokinase isoenzymes, muscle biopsy consistent with inflammatory myosi- tis). Laboratory features were defined as follows: thrombocytopenia (platelet count less than 100,000/mm3), leukopenia (white blood cell count less than 3,500/mm3), proteinuria (1 + on dipstick examination), and hematuria (urinary sediment with greater than 5 red blood cells per high power field). Many, but not all. of these patients were seen and followed by the authors. Based on the clinical findings, patients were classified with respect to 11 diseases or categories. Eighty-six patients met at least 4 of the 14 preliminary criteria set by the American Rheumatism Association (ARA) for SLE (13). Three patients with cutaneous LE (i.e., discoid lupus erythe- Table 2. Laboratory features in 150 patients with antibodies to Sm and/or ribonucleoprotein (RNP) Anti-Sm Anti-RNP and anti- Anti-Sm (%) (%) RNP (%) Feature* (42 patients) (76 patients) (32 patients) Thromboc ytopenia Leukopenia Proteinuriat Hernaturiat 36 I1 19 Anti-dsDNAB Anti-ssDNAB Anti-NPI ANA positive speckled non-speckled ANA negative Mean ANA titer (2 SD) 1, ? 1, Mean CH5O (* SD) ? 65 I64 * Anti-dsDNA = anti-double-stranded DNA; anti-ssdna = anti-single-stranded DNA; anti-np = anti-nuclear protein; ANA = antinuclear antibody. f P = anti-srn versus anti-rnp. $ P = anti-sm versus anti-rnp. 8 P = O.OOO1 anti-sm versus anti-rnp. 7 Speckled versus non-speckled. P = 0.04.

3 850 MUNVES AND SCHUR matosus) had characteristic erythernatosus plaques or papules (14) that spread outward, leaving central areas of hyperkeratosis and follicular plugging and atrophy, with no other signs and symptoms suggesting SLE. Twelve patients with drug-induced lupus developed symptoms after receiving either Aldomet (1 patient), hydralazine (4 patients), procainamide (5 patients), quinidine (1 patient), or Dilantin (1 patient). Seventeen patients had either definite or classic rheumatoid arthritis (RA) (15). Three patients met the criteria for juvenile arthritis (JA) suggested by the ARA (16). On the basis of overlapping features of SLE, polymyositis, and progressive systemic sclerosis (PSS) (3), MCTD was diagnosed in 4 patients, all of whom had antibodies to RNP. Two patients had Raynaud s disease (paroxysmal vasospasm of fingers and/or toes) with no accompanying connective tissue disease (i.e., PSS, SLE). Two patients had PSS based on preliminary criteria set by Masi et a1 (17). Six patients had miscellaneous rheumatic diseases: 2 had soft tissue rheumatism, 1 each had cutaneous vasculitis, gout, osteoarthritis of the lumbar spine, and polyarteritis nodosa. Eight patients had undifferentiated connective tissue disease syndromes, including: 1) arthritis/arthralgias, pleuropericarditis, and Raynaud s; 2) arthralgia and skin rash; 3) arthralgias, skin rash, and Raynaud s; 4) leukopenia, myalgia, fever, and fatigue; 5) cutaneous lupus and RA; 6) vasculitis, Raynaud s, arthritis, and Sjogren s syndrome; 7) arthritis and arthralgias; and 8) arthritislarthralgias, skin rash, and photosensitivity. Because criteria were insufficient, these 8 patients could not be classified as having one distinct entity. Seven patients had miscellaneous nonrheumatic diseases: 1 each had congestive heart failure, Parkinson s disease, asthma, lymphoma, idiopathic thrombocytopenic purpura, hemolytic anemia, and mitral valve prolapse. ANA were detected by immunofluorescence, utilizing cryostat sections of mouse liver as substrate and fluorescein-conjugated goat anti-ig (18). Anti-Sm and anti-rnp (and anti-single-stranded DNA and anti-nuclear proteins) were detected by counterimmunoelectrophoresis, using a method described in a previous publication (18) and recently restandardized using reference sera (19). Antibodies to double-stranded DNA were tested by imrnunofluorescence utilizing Crirhidia luciliae as the substrate (20). Total serum hemolytic complement (CH50) was determined by the method of Kent and Fife (21). RESULTS Forty-two serum samples from the 150 patients studied were found to contain anti-sm alone, 76 contained anti-rnp alone, and 32 contained both antibodies. Arthritis occurred with somewhat greater frequency (chi-square = 3.95, P = 0.05) among the patients with antibodies to Sm, compared with those having antibodies to RNP (Table 1). Patients with anti-sm were more likely to have proteinuria (chi-square = 8.89, P = 0.003) or hematuria (chi-square = 10.94, P = 0.001) than were patients with anti-rnp. Further- more, more patients with anti-sm had anti-doublestranded DNA (anti-dsdna)(chi-square = P = O.OOOOl), anti-single-stranded DNA (anti-ssdna) (chi-square = 42.75, P = O.OOOOl), and anti-nuclear protein (anti-np) (chi-square = 20.72, P = ) than did those with anti-rnp (Table 2). Mean CH50 was significantly lower in patients with anti-sm (168 * 63) than in those with anti-rnp (204? 65). With regard to the mean ANA titer, there was no significant difference between the group of patients with anti-sm and the group with anti-rnp. However, the speckled ANA pattern was found somewhat more frequently in the patients with anti-rnp (chi-square = 4.13, P = 0.04) (Table 2). There was no difference in the frequency of thrombocytopenia or leukopenia between the patients with anti-sm and those with anti- RNP (Table 2). Most of the patients who had antibodies to Sm, RNP, or both had SLE (Table 3). Antibodies to Sm were also seen in 5 patients with drug-induced lupus, 8 with RA, 2 with JA, 2 with MCTD, I with Raynaud s, 1 with PSS, I with gout, 4 with undifferentiated connective tissue disease, and 3 with miscellaneous nonrheumatic diseases-while most of these patients had only anti-sm, some had anti-rnp in addition (see Table 3). Antibodies to RNP were seen in all the conditions listed, but were found in particular in every patient with MCTD, Raynaud s disease, and PSS (Table 3). All patients with MCTD, Raynaud s disease, and PSS had a speckled ANA pattern. The highest mean ANA titers were found in MCTD and Raynaud s disease. DISCUSSION The purpose of this study was to determine the clinical associations and diagnostic specificity of the presence of antibodies to Sm and RNP in patients suspected of having rheumatic diseases. We studied the charts of 150 consecutive patients with antibodies to Sm, RNP, or both, irrespective of diagnosis, ANA test results, or clinical features. Few clinical differences were found between patients with antibodies to Sm and those with antibodies to RNP. No distinguishing clinical features were associated with the presence of anti-rnp. Patients with anti-sm, however, had a greater incidence of renal disease, antibodies to dsdna, ssdna, and NP, and lower total hemolytic complement levels than did patients with anti-rnp. The association between anti- Sm and anti-dsdna may, in part, be genetically

4 ~~ ~~ ANTIBODIES TO Sm AND RNP 85 1 Table 3. Diagnoses in 150 patients with antibodies to Sm and/or ribonucleoprotein (RNP) Anti-Srn and Anti-Sm Anti-RNP anti-rnp Diagnosis (42 patients) (76 patients) (32 patients) Systemic lupus erythematous Cutaneous lupus Drug-induced lupus Rheumatoid arthritis Juvenile arthritis Mixed connective tissue disease Raynaud s disease Progressive systemic sclerosis Miscellaneous rheumatic disease Undifferentiated connective tissue disease Miscellaneous nonrheumatic disease influenced, since both these antibodies are significantly associated with HLA-DR7 in patients with SLE (22). Other investigators have noted associations between anti-rnp and Raynaud s disease (3-Y), myositis (3,5-Y), and esophageal (3,8,9.23) or pulmonary (8-10) involvement. Patients with anti-sm were more likely to have CNS disease (5,6,9,24) or renal disease (3,5,6,8,9,11,12,24-26) than were patients with anti- RNP. The reported association in these other studies between anti-rnp and the clinical features cited above may have been due to the large number of patients selected with MCTD-a condition characterized by these signs and symptoms. In contrast, patients in our study were originally selected because they were suspected of having a rheumatic or a connective tissue syndrome that was not necessarily defined. The fact that we found no diseases associated with anti-rnp may be due to the large number and greater diversity of our patients. We did confirm the association between anti-sm and renal disease found in other studies. Moreover, the association of anti-sm with anti-dsdna and hypocomplementia-known markers of lupus nephritis-was not surprising. We have also examined the diagnostic specificity of these antibodies. Although the majority of our patients who had one or both of these antibodies had SLE, neither type of antibody was found exclusively in one particular disease. SLE was diagnosed in two-thirds of the patients with anti-sm, but this antibody was also found in a small percentage of patients with drug-induced lupus, RA, JA, MCTD, Raynaud s, PSS, miscellaneous rheumatic disease, undifferentiated connective tissue disease, and miscellaneous nonrheumatic disease. Some investigators have previously reported that anti-sm is found exclusively in SLE (3,6,1 I,25), although others have found this antibody in other rheumatic diseases (5,26,27). Although anti-sm was not 100% diagnostic for SLE, it is possible that if the patients with anti-sm and other diagnoses were followed long enough, they might eventually be found to develop SLE. While Sharp and others (3.6,8,9) have proposed the diagnostic specificity of anti-rnp for MCTD (an entity with overlapping features of SLE, polymyositis, and PSS), others, including ourselves, have also found anti-rnp in a variety of disorders, including SLE, PSS. RA, Raynaud s disease, and other overlap syndromes (2,4-8.1 I, 12,25,26,28). In fact, in the followup study by Nimelstein and coworkers of their initially described patients, it was shown that these patients developed different symptoms and diseases as time progressed (29). Sharp et al have also suggested that a majority of patients with high titers of speckled ANA have antibodies to RNP (3,6,9). We found that not everyone with a speckled ANA pattern had anti-sm or anti- RNP. and conversely, not everyone with anti-sm or anti-rnp had a speckled ANA pattern. However, in our experience, patients with anti-rnp were more likely to show this pattern (P = 0.04) than were those with anti-sm. In addition, we found anti-sm and anti- RNP in patients with both high- and low-titer ANA. These observations suggest that if one selects only those patients with high titers of speckled ANA, one

5 852 MUNVES AND SCHUR will fail to detect a sizable number of patients with anti-sm and/or anti-rnp. This approach may also limit selection to those patients with certain clinical features (3,6,8,9,26) and risks overinterpretation of the association of anti-sm and/or anti-rnp with particular clinical conditions or diseases. This study also points out the difficulty in determining the diagnostic specificity of ANA titers and/or patterns and their clinical associations. Virtually all other studies cited in this paper analyzed either sera from patients with established diagnoses or sera selected for high-titer or speckled ANA. In this study we examined a wide spectrum of patients, including anyone who might have a rheumatic or connective tissue disease. One should note that ANA testing is ordered at our institution whenever symptoms are in any way suggestive of a rheumatic or connective tissue disease. Selection of such a broad group of patients with diverse symptoms and signs probably accounts for the relatively small number of associations or diagnostic specificities noted here. Furthermore, this observation suggests that when one attempts to define the associations and diagnostic specificities of certain antibodies, it is important to study a large group of patients with diverse symptoms. ACKNOWLEDGMENTS We gratefully acknowledge the excellent technical assistance of Ms J. Gentile and Mr. T. McDermott REFERENCES Tan EM, Kunkel HG: Characteristics of a soluble nuclear antigen precipitating with sera of patients with systemic lupus erythematosus. J Immunol96: , 1966 Mattioli M, Reichlin M: Characterization of a soluble nuclear ribonucleoprotein antigen reactive with systemic lupus erythematosus sera. J Immunol 187: , 1971 Sharp GC, Irvin WS, Tan EM. Could RG, Holman HR: Mixed connective tissue disease: an apparently distinct rheumatic disease syndrome associated with a specific antibody to an extractable nuclear antigen (ENA). Am J Med 52: , 1972 Grennan DM, Bunn C, Hughes GRV, Buchanan WW, Dick WE: Frequency and clinical significance of antibodies to ribonucleoprotein in SLE and other connective tissue disease subgroups. Ann Rheum Dis 36: , 1977 Jonsson J, Norberg R: Symptomatology and diagnosis in connective tissue disease. Scand J Rheumatol 7: , Sharp GC, Irvin WS, May CM, Holman HR, McDuffie FC, Hess EV, Schmid FR: Association of antibodies to ribonucleoprotein and Sm antigens with mixed connective tissue disease, systemic lupus erythematosus, and other rheumatic diseases. N Engl J Med 295: , Parker MD: Ribonucleoprotein antibodies: frequency and clinical significance in systemic lupus erythematosus, scleroderma, and mixed connective tissue disease. J Lab Clin Med 82: , Bennett R, O Connell D: Mixed connective tissue disease: a clinicopathologic study of 20 cases. Semin Arthritis Rheum 10:25-51, Sharp GC: Mixed connective tissue disease: current concepts. Arthritis Rheum (suppl) 20:s 18 I-S186, Grant KD, Adams LE, Hess EV: MCTD: mixed connective tissue disease-a subset with sequential clinical and laboratory features. J Rheumatol Hamburger M, Hodes S, Barland P: The incidence and clinical significance of antibodies to extractable nuclear antigens. Am J Med Sci 273:21-28, Notman DD, Kurata N, Tan EM: Profiles of antinuclear antibodies in systemic rheumatic diseases. Ann Intern Med 83: , Cohen AS, Reynolds WE, Franklin EC, Kulka JP, Ropes MW, Shulman LE, Wallace SL: Preliminary criteria for the ciassification of systemic lupus erythematosus. Bull Rheum Dis 21: , Rothfield NF: Systemic lupus erythematosus: clinical and laboratory aspects, Arthritis and Allied Conditions. Ninth edition. Edited by DJ McCarty. Philadelphia, Lea & Febiger, 1979, pp Ropes MW, Bennett GA, Cobb S, Jacox R, Jessar RA: 1958 revision of diagnostic criteria for rheumatoid arthritis. Bull Rheum Dis 9: , Brewer EJ Jr, Bass J. Baum J, Cassidy JT, Fink C, Jacobs J, Hanson V, Levinson JE, Schaller J, Stillman JS: Current proposed revision of JRA criteria. Arthritis Rheum (suppl) 20: , Masi AT, Rodnan GP, Medsger TA Jr, Altman RD, D Angelo WA, Fries JF, LeRoy EC, Kirsner AB, Mac- Kenzie AH, McShane DJ, Myers AR, Sharp GC: Preliminary criteria for the classification of systemic sclerosis (scleroderma). Bull Rheum Dis 31:l-6, Schur PH, DeAngelis D. Jackson JM: Immunological detection of nucleic acid and antibodies to nucleic acids and nuclear antigens by counterimmunoelectrophoresis. Clin Exp Immunol 17: , Tan EM, Fritzler MJ, McDougal JS, McDuffie FC, Nakamura RM, Reichlin M, Reimer CB, Sharp GC, Schur PH, Wilson MR, Winchester RJ: Reference sera for antinuclear antibodies. I. Antibodies to native DNA, Sm, nuclear RNP, and SS-BILa. Arthritis Rheum 25: , Arden LA, DeGroot ER, Feltkamp TEW: Immunology of DNA Crithidia luciliae, a simple substrate for the

6 ANTIBODIES TO Sm AND RNP 853 determination of anti-dsdna with the immunofluorescent technique. Proc NY Acad Sci , Kent JF, Fife EH: Precise standardization of reagents for complement fixation. Am J Trop Med Hyg 12: , Schur PH, Meyer I, Garovoy M, Carpenter CB: Associations between systemic lupus erythematosus and the major histocompatibility complex: clinical and immunological considerations. Clin Immunol Immunopathol 24~ , Winn D, Gerhardt D, Winship D, Sharp G: Esophageal function in steroid treated patients with mixed connective tissue disease (MCTD) (abstract). Clin Res 24:545A, Harmon C, Wolfe F, Lillard S, Held C, Cordon R, Sharp GC: Pulmonary involvement in mixed connective tissue disease (MCTD) (abstract). Arthritis Rheum 19:801, Barada FA Jr, Andrews BS, Davis JS IV, Taylor RP: Antibodies to Sm in patients with systemic lupus erythematosus: correlation of Sm antibody titers with disease activity and other laboratory parameters. Arthritis Rheum 24:123&1244, Reichlin M, Mattioli M: Correlation of a precipitin reaction to a RNA protein antigen and a low prevalence of nephritis in patients with systemic lupus erythematosus. N Engl J Med 286: , Gaudreau A, Amor B, Kahn MF, Ryckewaert A, Sany J, Peltier AP: Clinical significance of antibodies to soluble extractable nuclear antigens (anti-ena). Ann Rheum Dis 37: , Alarcon-Segovia D, Fishbein E, Reyes PA, Dies H, Shwadsky S: Antinuclear antibodies in patients on anticonvulsant therapy. Clin Exp Immunol 12:39-47, Nimelstein S, Brody S, McShane D, Holman HR: Mixed connective tissue disease: a subsequent evaluation of the original 25 patients. Medicine 59: , 1980 Third Annual Musculoskeletal and Orthopedic Radiology Seminar August 15-19, 1983, Broadrnoor Hotel, Colorado Springs, CO, sponsored by the Department of Radiology, Hospital of the University of Pennsylvania. 24 hours of Category I credit. Contact Ms Janice Ford, CME Coordinator, Dept. of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA