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Thomas A. Medsger - One of the best experts on this subject based on the ideXlab platform.
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anti u11 u12 RNP antibodies in systemic sclerosis a new serologic marker associated with pulmonary fibrosis
Arthritis & Rheumatism, 2009Co-Authors: Noreen Fertig, Mary Lucas, Thomas A. Medsger, Robyn T Domsic, Tatiana S Rodriguezreyna, Masataka Kuwana, Carol FeghalibostwickAbstract:Objective To characterize a new serum autoantibody in patients with systemic sclerosis (SSc) directed against U11/U12 RNP and to identify the clinical features associated with this autoantibody. Methods We identified autoantibodies directed against the U11/U12 RNP complex in sera of patients with SSc and confirmed antibody specificity by immunoprecipitation, reverse transcriptase–polymerase chain reaction, and Southern blotting. We determined the prevalence of these antibodies in SSc and their specificity for SSc. We compared anti–U11/U12 RNP autoantibody–positive and negative SSc patients on demographic, disease classification, clinical variables, and survival. Results We identified 33 patients with anti–U11/U12 RNP antibodies. In 2 consecutive series of SSc patients first seen at 10-year intervals (1994–1995 and 2004–2005), the prevalence of anti–U11/U12 RNP antibody–positive patients was 15 of 462 (3.2%). Seventeen (52%) of these 33 patients had limited cutaneous involvement. All patients had Raynaud's phenomenon and 82% had gastrointestinal (GI) involvement. None had “intrinsic” pulmonary arterial hypertension. The most significant clinical difference between anti–U11/U12 antibody–positive and negative cohorts was the prevalence of lung fibrosis, which occurred in 79% of the anti–U11/U12 RNP antibody–positive patients versus 37% of the anti–U11/U12 RNP antibody–negative patients (P < 0.0001). GI involvement was also significantly increased in the anti–U11/U12 RNP antibody–positive group. Patients with anti–U11/U12 RNP antibodies and pulmonary fibrosis had a 2.25-fold greater risk of death than anti–U11/U12 RNP negative patients with pulmonary fibrosis. Conclusion Anti–U11/U12 RNP antibodies are present in the sera of approximately 3% of patients with SSc and are a marker for lung fibrosis, which is often severe.
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anti u3 RNP autoantibodies in systemic sclerosis
Arthritis & Rheumatism, 2009Co-Authors: Rohit Aggarwal, Mary Lucas, Noreen Fertig, Chester V. Oddis, Thomas A. MedsgerAbstract:Objective To describe the classification, demographic and clinical features, and survival in anti–U3 RNP autoantibody–positive patients with systemic sclerosis (SSc). Methods Medical records of 108 anti–U3 RNP–positive and 2,471 anti–U3 RNP–negative SSc patients first evaluated during 1985–2003 were reviewed. Anti–U3 RNP antibody was detected by protein and RNA immunoprecipitation. Disease classification, demographic and clinical features, organ system involvement, and survival were compared between the 2 patient groups, by Student's t-test, chi-square analysis, and Mantel-Haenszel test. Results The anti–U3 RNP–positive group had a higher proportion of African American patients (27% versus 5%; P < 0.001) and male patients (29% versus 19%; P = 0.021), and was younger at the time of first physician diagnosis (mean age 42.8 years versus 47.4 years; P = 0.001). The 2 groups had similar proportions of patients with diffuse cutaneous involvement (47% and 45% in those with and those without anti–U3 RNP, respectively). However, among patients with diffuse cutaneous involvement, the mean maximum modified Rodnan skin score was significantly lower in the anti–U3 RNP group (22.3 versus 27.9; P < 0.001). Skeletal muscle involvement was more frequent in anti–U3 RNP–positive patients (25% versus 14%; P = 0.002), as was “intrinsic” pulmonary arterial hypertension (PAH) (31% versus 13%; P < 0.001). The frequency of gastrointestinal involvement, cardiac involvement, pulmonary fibrosis, and “renal crisis” did not differ significantly between the 2 groups. Survival was worse in the anti–U3 RNP–positive group (hazard ratio 1.38 [95% confidence interval 1.05–1.82]). PAH was the most common known cause of death in patients with anti–U3 RNP (30%, versus 10% in the anti–U3 RNP–negative group; P < 0.001). Conclusion The present findings demonstrate that the frequencies of African American race and male sex are greater among SSc patients with anti–U3 RNP antibody than those without, and the former group is younger at SSc diagnosis. Anti–U3 RNP–positive patients have more frequent skeletal muscle involvement and PAH, the latter being the most common cause of death.
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Anti-U3 RNP Autoantibodies in Systemic Sclerosis
Arthritis and rheumatism, 2009Co-Authors: Rohit Aggarwal, Mary Lucas, Noreen Fertig, Chester V. Oddis, Thomas A. MedsgerAbstract:To describe the classification, demographic and clinical features, and survival in anti-U3 RNP autoantibody-positive patients with systemic sclerosis (SSc). Medical records of 108 anti-U3 RNP-positive and 2,471 anti-U3 RNP-negative SSc patients first evaluated during 1985-2003 were reviewed. Anti-U3 RNP antibody was detected by protein and RNA immunoprecipitation. Disease classification, demographic and clinical features, organ system involvement, and survival were compared between the 2 patient groups, by Student's t-test, chi-square analysis, and Mantel-Haenszel test. The anti-U3 RNP-positive group had a higher proportion of African American patients (27% versus 5%; P < 0.001) and male patients (29% versus 19%; P = 0.021), and was younger at the time of first physician diagnosis (mean age 42.8 years versus 47.4 years; P = 0.001). The 2 groups had similar proportions of patients with diffuse cutaneous involvement (47% and 45% in those with and those without anti-U3 RNP, respectively). However, among patients with diffuse cutaneous involvement, the mean maximum modified Rodnan skin score was significantly lower in the anti-U3 RNP group (22.3 versus 27.9; P < 0.001). Skeletal muscle involvement was more frequent in anti-U3 RNP-positive patients (25% versus 14%; P = 0.002), as was "intrinsic" pulmonary arterial hypertension (PAH) (31% versus 13%; P < 0.001). The frequency of gastrointestinal involvement, cardiac involvement, pulmonary fibrosis, and "renal crisis" did not differ significantly between the 2 groups. Survival was worse in the anti-U3 RNP-positive group (hazard ratio 1.38 [95% confidence interval 1.05-1.82]). PAH was the most common known cause of death in patients with anti-U3 RNP (30%, versus 10% in the anti-U3 RNP-negative group; P < 0.001). The present findings demonstrate that the frequencies of African American race and male sex are greater among SSc patients with anti-U3 RNP antibody than those without, and the former group is younger at SSc diagnosis. Anti-U3 RNP-positive patients have more frequent skeletal muscle involvement and PAH, the latter being the most common cause of death.
Noreen Fertig - One of the best experts on this subject based on the ideXlab platform.
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anti u11 u12 RNP antibodies in systemic sclerosis a new serologic marker associated with pulmonary fibrosis
Arthritis & Rheumatism, 2009Co-Authors: Noreen Fertig, Mary Lucas, Thomas A. Medsger, Robyn T Domsic, Tatiana S Rodriguezreyna, Masataka Kuwana, Carol FeghalibostwickAbstract:Objective To characterize a new serum autoantibody in patients with systemic sclerosis (SSc) directed against U11/U12 RNP and to identify the clinical features associated with this autoantibody. Methods We identified autoantibodies directed against the U11/U12 RNP complex in sera of patients with SSc and confirmed antibody specificity by immunoprecipitation, reverse transcriptase–polymerase chain reaction, and Southern blotting. We determined the prevalence of these antibodies in SSc and their specificity for SSc. We compared anti–U11/U12 RNP autoantibody–positive and negative SSc patients on demographic, disease classification, clinical variables, and survival. Results We identified 33 patients with anti–U11/U12 RNP antibodies. In 2 consecutive series of SSc patients first seen at 10-year intervals (1994–1995 and 2004–2005), the prevalence of anti–U11/U12 RNP antibody–positive patients was 15 of 462 (3.2%). Seventeen (52%) of these 33 patients had limited cutaneous involvement. All patients had Raynaud's phenomenon and 82% had gastrointestinal (GI) involvement. None had “intrinsic” pulmonary arterial hypertension. The most significant clinical difference between anti–U11/U12 antibody–positive and negative cohorts was the prevalence of lung fibrosis, which occurred in 79% of the anti–U11/U12 RNP antibody–positive patients versus 37% of the anti–U11/U12 RNP antibody–negative patients (P < 0.0001). GI involvement was also significantly increased in the anti–U11/U12 RNP antibody–positive group. Patients with anti–U11/U12 RNP antibodies and pulmonary fibrosis had a 2.25-fold greater risk of death than anti–U11/U12 RNP negative patients with pulmonary fibrosis. Conclusion Anti–U11/U12 RNP antibodies are present in the sera of approximately 3% of patients with SSc and are a marker for lung fibrosis, which is often severe.
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anti u3 RNP autoantibodies in systemic sclerosis
Arthritis & Rheumatism, 2009Co-Authors: Rohit Aggarwal, Mary Lucas, Noreen Fertig, Chester V. Oddis, Thomas A. MedsgerAbstract:Objective To describe the classification, demographic and clinical features, and survival in anti–U3 RNP autoantibody–positive patients with systemic sclerosis (SSc). Methods Medical records of 108 anti–U3 RNP–positive and 2,471 anti–U3 RNP–negative SSc patients first evaluated during 1985–2003 were reviewed. Anti–U3 RNP antibody was detected by protein and RNA immunoprecipitation. Disease classification, demographic and clinical features, organ system involvement, and survival were compared between the 2 patient groups, by Student's t-test, chi-square analysis, and Mantel-Haenszel test. Results The anti–U3 RNP–positive group had a higher proportion of African American patients (27% versus 5%; P < 0.001) and male patients (29% versus 19%; P = 0.021), and was younger at the time of first physician diagnosis (mean age 42.8 years versus 47.4 years; P = 0.001). The 2 groups had similar proportions of patients with diffuse cutaneous involvement (47% and 45% in those with and those without anti–U3 RNP, respectively). However, among patients with diffuse cutaneous involvement, the mean maximum modified Rodnan skin score was significantly lower in the anti–U3 RNP group (22.3 versus 27.9; P < 0.001). Skeletal muscle involvement was more frequent in anti–U3 RNP–positive patients (25% versus 14%; P = 0.002), as was “intrinsic” pulmonary arterial hypertension (PAH) (31% versus 13%; P < 0.001). The frequency of gastrointestinal involvement, cardiac involvement, pulmonary fibrosis, and “renal crisis” did not differ significantly between the 2 groups. Survival was worse in the anti–U3 RNP–positive group (hazard ratio 1.38 [95% confidence interval 1.05–1.82]). PAH was the most common known cause of death in patients with anti–U3 RNP (30%, versus 10% in the anti–U3 RNP–negative group; P < 0.001). Conclusion The present findings demonstrate that the frequencies of African American race and male sex are greater among SSc patients with anti–U3 RNP antibody than those without, and the former group is younger at SSc diagnosis. Anti–U3 RNP–positive patients have more frequent skeletal muscle involvement and PAH, the latter being the most common cause of death.
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Anti-U3 RNP Autoantibodies in Systemic Sclerosis
Arthritis and rheumatism, 2009Co-Authors: Rohit Aggarwal, Mary Lucas, Noreen Fertig, Chester V. Oddis, Thomas A. MedsgerAbstract:To describe the classification, demographic and clinical features, and survival in anti-U3 RNP autoantibody-positive patients with systemic sclerosis (SSc). Medical records of 108 anti-U3 RNP-positive and 2,471 anti-U3 RNP-negative SSc patients first evaluated during 1985-2003 were reviewed. Anti-U3 RNP antibody was detected by protein and RNA immunoprecipitation. Disease classification, demographic and clinical features, organ system involvement, and survival were compared between the 2 patient groups, by Student's t-test, chi-square analysis, and Mantel-Haenszel test. The anti-U3 RNP-positive group had a higher proportion of African American patients (27% versus 5%; P < 0.001) and male patients (29% versus 19%; P = 0.021), and was younger at the time of first physician diagnosis (mean age 42.8 years versus 47.4 years; P = 0.001). The 2 groups had similar proportions of patients with diffuse cutaneous involvement (47% and 45% in those with and those without anti-U3 RNP, respectively). However, among patients with diffuse cutaneous involvement, the mean maximum modified Rodnan skin score was significantly lower in the anti-U3 RNP group (22.3 versus 27.9; P < 0.001). Skeletal muscle involvement was more frequent in anti-U3 RNP-positive patients (25% versus 14%; P = 0.002), as was "intrinsic" pulmonary arterial hypertension (PAH) (31% versus 13%; P < 0.001). The frequency of gastrointestinal involvement, cardiac involvement, pulmonary fibrosis, and "renal crisis" did not differ significantly between the 2 groups. Survival was worse in the anti-U3 RNP-positive group (hazard ratio 1.38 [95% confidence interval 1.05-1.82]). PAH was the most common known cause of death in patients with anti-U3 RNP (30%, versus 10% in the anti-U3 RNP-negative group; P < 0.001). The present findings demonstrate that the frequencies of African American race and male sex are greater among SSc patients with anti-U3 RNP antibody than those without, and the former group is younger at SSc diagnosis. Anti-U3 RNP-positive patients have more frequent skeletal muscle involvement and PAH, the latter being the most common cause of death.
Mary Lucas - One of the best experts on this subject based on the ideXlab platform.
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anti u11 u12 RNP antibodies in systemic sclerosis a new serologic marker associated with pulmonary fibrosis
Arthritis & Rheumatism, 2009Co-Authors: Noreen Fertig, Mary Lucas, Thomas A. Medsger, Robyn T Domsic, Tatiana S Rodriguezreyna, Masataka Kuwana, Carol FeghalibostwickAbstract:Objective To characterize a new serum autoantibody in patients with systemic sclerosis (SSc) directed against U11/U12 RNP and to identify the clinical features associated with this autoantibody. Methods We identified autoantibodies directed against the U11/U12 RNP complex in sera of patients with SSc and confirmed antibody specificity by immunoprecipitation, reverse transcriptase–polymerase chain reaction, and Southern blotting. We determined the prevalence of these antibodies in SSc and their specificity for SSc. We compared anti–U11/U12 RNP autoantibody–positive and negative SSc patients on demographic, disease classification, clinical variables, and survival. Results We identified 33 patients with anti–U11/U12 RNP antibodies. In 2 consecutive series of SSc patients first seen at 10-year intervals (1994–1995 and 2004–2005), the prevalence of anti–U11/U12 RNP antibody–positive patients was 15 of 462 (3.2%). Seventeen (52%) of these 33 patients had limited cutaneous involvement. All patients had Raynaud's phenomenon and 82% had gastrointestinal (GI) involvement. None had “intrinsic” pulmonary arterial hypertension. The most significant clinical difference between anti–U11/U12 antibody–positive and negative cohorts was the prevalence of lung fibrosis, which occurred in 79% of the anti–U11/U12 RNP antibody–positive patients versus 37% of the anti–U11/U12 RNP antibody–negative patients (P < 0.0001). GI involvement was also significantly increased in the anti–U11/U12 RNP antibody–positive group. Patients with anti–U11/U12 RNP antibodies and pulmonary fibrosis had a 2.25-fold greater risk of death than anti–U11/U12 RNP negative patients with pulmonary fibrosis. Conclusion Anti–U11/U12 RNP antibodies are present in the sera of approximately 3% of patients with SSc and are a marker for lung fibrosis, which is often severe.
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anti u3 RNP autoantibodies in systemic sclerosis
Arthritis & Rheumatism, 2009Co-Authors: Rohit Aggarwal, Mary Lucas, Noreen Fertig, Chester V. Oddis, Thomas A. MedsgerAbstract:Objective To describe the classification, demographic and clinical features, and survival in anti–U3 RNP autoantibody–positive patients with systemic sclerosis (SSc). Methods Medical records of 108 anti–U3 RNP–positive and 2,471 anti–U3 RNP–negative SSc patients first evaluated during 1985–2003 were reviewed. Anti–U3 RNP antibody was detected by protein and RNA immunoprecipitation. Disease classification, demographic and clinical features, organ system involvement, and survival were compared between the 2 patient groups, by Student's t-test, chi-square analysis, and Mantel-Haenszel test. Results The anti–U3 RNP–positive group had a higher proportion of African American patients (27% versus 5%; P < 0.001) and male patients (29% versus 19%; P = 0.021), and was younger at the time of first physician diagnosis (mean age 42.8 years versus 47.4 years; P = 0.001). The 2 groups had similar proportions of patients with diffuse cutaneous involvement (47% and 45% in those with and those without anti–U3 RNP, respectively). However, among patients with diffuse cutaneous involvement, the mean maximum modified Rodnan skin score was significantly lower in the anti–U3 RNP group (22.3 versus 27.9; P < 0.001). Skeletal muscle involvement was more frequent in anti–U3 RNP–positive patients (25% versus 14%; P = 0.002), as was “intrinsic” pulmonary arterial hypertension (PAH) (31% versus 13%; P < 0.001). The frequency of gastrointestinal involvement, cardiac involvement, pulmonary fibrosis, and “renal crisis” did not differ significantly between the 2 groups. Survival was worse in the anti–U3 RNP–positive group (hazard ratio 1.38 [95% confidence interval 1.05–1.82]). PAH was the most common known cause of death in patients with anti–U3 RNP (30%, versus 10% in the anti–U3 RNP–negative group; P < 0.001). Conclusion The present findings demonstrate that the frequencies of African American race and male sex are greater among SSc patients with anti–U3 RNP antibody than those without, and the former group is younger at SSc diagnosis. Anti–U3 RNP–positive patients have more frequent skeletal muscle involvement and PAH, the latter being the most common cause of death.
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Anti-U3 RNP Autoantibodies in Systemic Sclerosis
Arthritis and rheumatism, 2009Co-Authors: Rohit Aggarwal, Mary Lucas, Noreen Fertig, Chester V. Oddis, Thomas A. MedsgerAbstract:To describe the classification, demographic and clinical features, and survival in anti-U3 RNP autoantibody-positive patients with systemic sclerosis (SSc). Medical records of 108 anti-U3 RNP-positive and 2,471 anti-U3 RNP-negative SSc patients first evaluated during 1985-2003 were reviewed. Anti-U3 RNP antibody was detected by protein and RNA immunoprecipitation. Disease classification, demographic and clinical features, organ system involvement, and survival were compared between the 2 patient groups, by Student's t-test, chi-square analysis, and Mantel-Haenszel test. The anti-U3 RNP-positive group had a higher proportion of African American patients (27% versus 5%; P < 0.001) and male patients (29% versus 19%; P = 0.021), and was younger at the time of first physician diagnosis (mean age 42.8 years versus 47.4 years; P = 0.001). The 2 groups had similar proportions of patients with diffuse cutaneous involvement (47% and 45% in those with and those without anti-U3 RNP, respectively). However, among patients with diffuse cutaneous involvement, the mean maximum modified Rodnan skin score was significantly lower in the anti-U3 RNP group (22.3 versus 27.9; P < 0.001). Skeletal muscle involvement was more frequent in anti-U3 RNP-positive patients (25% versus 14%; P = 0.002), as was "intrinsic" pulmonary arterial hypertension (PAH) (31% versus 13%; P < 0.001). The frequency of gastrointestinal involvement, cardiac involvement, pulmonary fibrosis, and "renal crisis" did not differ significantly between the 2 groups. Survival was worse in the anti-U3 RNP-positive group (hazard ratio 1.38 [95% confidence interval 1.05-1.82]). PAH was the most common known cause of death in patients with anti-U3 RNP (30%, versus 10% in the anti-U3 RNP-negative group; P < 0.001). The present findings demonstrate that the frequencies of African American race and male sex are greater among SSc patients with anti-U3 RNP antibody than those without, and the former group is younger at SSc diagnosis. Anti-U3 RNP-positive patients have more frequent skeletal muscle involvement and PAH, the latter being the most common cause of death.
Rohit Aggarwal - One of the best experts on this subject based on the ideXlab platform.
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anti u3 RNP autoantibodies in systemic sclerosis
Arthritis & Rheumatism, 2009Co-Authors: Rohit Aggarwal, Mary Lucas, Noreen Fertig, Chester V. Oddis, Thomas A. MedsgerAbstract:Objective To describe the classification, demographic and clinical features, and survival in anti–U3 RNP autoantibody–positive patients with systemic sclerosis (SSc). Methods Medical records of 108 anti–U3 RNP–positive and 2,471 anti–U3 RNP–negative SSc patients first evaluated during 1985–2003 were reviewed. Anti–U3 RNP antibody was detected by protein and RNA immunoprecipitation. Disease classification, demographic and clinical features, organ system involvement, and survival were compared between the 2 patient groups, by Student's t-test, chi-square analysis, and Mantel-Haenszel test. Results The anti–U3 RNP–positive group had a higher proportion of African American patients (27% versus 5%; P < 0.001) and male patients (29% versus 19%; P = 0.021), and was younger at the time of first physician diagnosis (mean age 42.8 years versus 47.4 years; P = 0.001). The 2 groups had similar proportions of patients with diffuse cutaneous involvement (47% and 45% in those with and those without anti–U3 RNP, respectively). However, among patients with diffuse cutaneous involvement, the mean maximum modified Rodnan skin score was significantly lower in the anti–U3 RNP group (22.3 versus 27.9; P < 0.001). Skeletal muscle involvement was more frequent in anti–U3 RNP–positive patients (25% versus 14%; P = 0.002), as was “intrinsic” pulmonary arterial hypertension (PAH) (31% versus 13%; P < 0.001). The frequency of gastrointestinal involvement, cardiac involvement, pulmonary fibrosis, and “renal crisis” did not differ significantly between the 2 groups. Survival was worse in the anti–U3 RNP–positive group (hazard ratio 1.38 [95% confidence interval 1.05–1.82]). PAH was the most common known cause of death in patients with anti–U3 RNP (30%, versus 10% in the anti–U3 RNP–negative group; P < 0.001). Conclusion The present findings demonstrate that the frequencies of African American race and male sex are greater among SSc patients with anti–U3 RNP antibody than those without, and the former group is younger at SSc diagnosis. Anti–U3 RNP–positive patients have more frequent skeletal muscle involvement and PAH, the latter being the most common cause of death.
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Anti-U3 RNP Autoantibodies in Systemic Sclerosis
Arthritis and rheumatism, 2009Co-Authors: Rohit Aggarwal, Mary Lucas, Noreen Fertig, Chester V. Oddis, Thomas A. MedsgerAbstract:To describe the classification, demographic and clinical features, and survival in anti-U3 RNP autoantibody-positive patients with systemic sclerosis (SSc). Medical records of 108 anti-U3 RNP-positive and 2,471 anti-U3 RNP-negative SSc patients first evaluated during 1985-2003 were reviewed. Anti-U3 RNP antibody was detected by protein and RNA immunoprecipitation. Disease classification, demographic and clinical features, organ system involvement, and survival were compared between the 2 patient groups, by Student's t-test, chi-square analysis, and Mantel-Haenszel test. The anti-U3 RNP-positive group had a higher proportion of African American patients (27% versus 5%; P < 0.001) and male patients (29% versus 19%; P = 0.021), and was younger at the time of first physician diagnosis (mean age 42.8 years versus 47.4 years; P = 0.001). The 2 groups had similar proportions of patients with diffuse cutaneous involvement (47% and 45% in those with and those without anti-U3 RNP, respectively). However, among patients with diffuse cutaneous involvement, the mean maximum modified Rodnan skin score was significantly lower in the anti-U3 RNP group (22.3 versus 27.9; P < 0.001). Skeletal muscle involvement was more frequent in anti-U3 RNP-positive patients (25% versus 14%; P = 0.002), as was "intrinsic" pulmonary arterial hypertension (PAH) (31% versus 13%; P < 0.001). The frequency of gastrointestinal involvement, cardiac involvement, pulmonary fibrosis, and "renal crisis" did not differ significantly between the 2 groups. Survival was worse in the anti-U3 RNP-positive group (hazard ratio 1.38 [95% confidence interval 1.05-1.82]). PAH was the most common known cause of death in patients with anti-U3 RNP (30%, versus 10% in the anti-U3 RNP-negative group; P < 0.001). The present findings demonstrate that the frequencies of African American race and male sex are greater among SSc patients with anti-U3 RNP antibody than those without, and the former group is younger at SSc diagnosis. Anti-U3 RNP-positive patients have more frequent skeletal muscle involvement and PAH, the latter being the most common cause of death.
Xavier Bossuyt - One of the best experts on this subject based on the ideXlab platform.
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Clinical Relevance of Measurement of Antibodies to Individual snU1-RNP Proteins
Clinical chemistry, 2005Co-Authors: Ariane Luyckx, R. Westhovens, Els Oris, Wolfgang Papisch, Xavier BossuytAbstract:Anti-ribonucleoprotein (RNP) antibodies are found in mixed connective tissue disease (MCTD), a syndrome characterized by features of systemic lupus erythematosus (SLE), inflammatory muscle disease, and scleroderma (1). High titers of anti-RNP antibodies support the diagnosis of MCTD, and testing should be ordered when the diagnosis is suspected (2). Anti-RNP antibodies are also found in rheumatic diseases such as SLE, Sjogren syndrome, rheumatoid arthritis, polymyositis, and systemic sclerosis (2). The antigens to which anti-RNP antibodies react reside in many proteins (70 kD, protein A, and protein C) complexed with small nuclear U1-RNA. This complex is called small nuclear U1 ribonucleoprotein (snU1-RNP). Similarly, the antigen to which anti-Sm antibodies bind is composed of a complex of proteins (B, B′, D, E, F, and G) and snRNAs (U1, U2, U4–U6, and U5). Anti-Sm antibodies are highly specific for SLE (2). The snRNPs (U1-RNP/Sm) are involved in the splicing of precursor messenger RNA. Traditionally, anti-RNP antibodies have been detected by techniques such as passive hemagglutination, immunodiffusion, counterimmunoelectrophoresis, and ELISA using purified antigen. More recently, recombinant antigens have been used increasingly to identify anti-RNP antibodies, thus allowing identification of antibodies to the individual proteins of the snU1-RNP complex (70 kD, protein …
