Coexistence of anti-RNA polymerase III and anti-U1RNP antibodies in patients with systemic lupus erythematosus: two cases without features of scleroderma.
Anti-RNA polymerase III (RNAP III) antibodies are highly specific for scleroderma (SSc) and associated with diffuse SSc and renal crisis. Coexistence of anti-RNAP III and other SSc autoantibodies is rarely documented. We report three cases with coexisting anti-RNAP III and anti-U1RNP. Autoantibodies in 3829 sera from rheumatology clinics were screened by immunoprecipitation. Anti-RNAP III-positive sera were also examined by immunofluorescence and anti-RNAP III ELISA. In total, 35 anti-RNAP III-positive sera were identified by immunoprecipitation, in which three had coexisting anti-U1RNP. All three were anti-RNAP III ELISA positive. Two had anti-RNAP I dominant (vs. RNAP III) reactivity and showed strong nucleolar staining. A case with anti-U1/U2RNP (U2RNP dominant) had systemic lupus erythematosus (SLE)-SSc overlap syndrome; however, the remaining two cases had SLE without signs of SSc. All three cases of anti-RNAP III + U1RNP fulfilled ACR SLE criteria but none in the group with anti-RNAP III alone (p = 0.0002). In contrast, only one case in the former group had sclerodermatous skin changes and Raynaud's phenomenon, vs. 92% with scleroderma in the latter (p < 0.05). Although anti-RNAP III is highly specific for SSc, cases with coexisting anti-U1RNP are not so uncommon among anti-RNAP III positives (8%, 3/35) and may be SLE without features of SSc.
Division of Rheumatology and Clinical Immunology, Department of Medicine, University of Florida, Gainesville, USA. minoru.satoh@medicine.ufl.edu
M
M
Satoh
M
M
Vazquez-Del Mercado
M E
ME
Krzyszczak
Y
Y
Li
A
A
Ceribelli
R W
RW
Burlingame
T T
TT
Webb
E S
ES
Sobel
W H
WH
Reeves
E K L
EK
Chan
D000328:Adult; D000974:Antibodies, Antinuclear / Q000097:blood*; D001323:Autoantibodies / Q000097:blood*; D005260:Female; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood / Q000276:immunology / Q000473:pathology; D012320:RNA Polymerase III / Q000276:immunology*; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000276:immunology*; D012595:Scleroderma, Systemic / Q000097:blood / Q000276:immunology*
D000974:Antibodies, Antinuclear; D001323:Autoantibodies; D017412:Ribonucleoprotein, U1 Small Nuclear; D012320:RNA Polymerase III