Clinical significance of antinuclear matrix antibody in serum from patients with anti-U1RNP antibody

Serum containing anti-U1RNP antibodies reacts with the nuclear matrix, the relatively insoluble component of the cell nucleus, in addition to U1RNP, I n this study, we determine the serum titer and clinical correlations of ant inuclear matrix antibodies in samples from patients with anti-U1RNP antibod ies. The patients with anti-U1RNP antibodies were classified as having mixe d connective tissue disease (MCTD, 15 patients), systemic sclerosis (SSc, 1 2 patients), systemic lupus erythematosus (SLE, 7 patients), and undifferen tiated CTD (UCTD, 9 patients). Antinuclear matrix antibodies were detected using indirect immunofluorescence staining on HCl-treated HEp-2 cells, The antinuclear matrix antibody titer was significantly higher in serum from pa tients with MCTD or SSc than in serum from patients with SLE or UCTD, The a ntinuclear matrix antibody titer was significantly increased in serum from patients with sclerodactyly, pitting scars, contracture of the phalanges, a nd decreased carbon monoxide diffusion capacity. Thus, a higher titer of an tinuclear matrix antibodies in serum from patients with anti-U1RNP antibodi es may be associated with a clinical diagnosis of MCTD or SSc rather than a diagnosis of SLE or UCTD.