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| Previous Nomenclature | Nucleolar speckled |
| Description | Densely distributed but distinct speckles in the nucleoli of interphase cells. In metaphase cells, up to 5 bright pairs of the nucleolar organizer region (NOR) can be seen as speckles in the chromatin mass. The cytoplasm of mitotic cells may be slightly positive |
| Antigen Association | RNA polymerase I (RNApol-I), NOR90/hUBF |
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Clinical Relevance
First level information About Clinical Relevance & List of Abbreviations |
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▶ The AC-10 pattern can be seen in various conditions, including systemic sclerosis (SSc), Raynaud’s phenomenon, Sjögren’s disease (SjD), and cancer [1-7] ▶ If the AC-10 pattern is observed, follow-up testing for NOR90 antibodies is to be considered; the antigen is included in disease specific immunoassays (i.e. SSc profile) [3, 4] ▶ NOR90 antibody associated with paraneoplastic SSc and with interstitial lung disease in SSc and idiopathic interstitial pneumonia patients [8, 9] ▶ While AC-10 is seen in sera with RNApol-III antibodies, this is thought to be due to concomitant reactivity with RNApol-I and/or RNApol-II antibodies. RNApol-III antibodies are also associated with mixed AC-4 and AC-5 patterns [10]; therefore, if SSc is clinically suspected, it is recommended to perform a follow-up test for RNApol-III antibodies; specific immunoassays for RNApol-I or RNApol-II antibodies are currently not commercially available [1, 2] |
| Second level information |
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None |
| References |
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1. Reimer G, Rose KM, Scheer U, Tan EM. Autoantibody to RNA polymerase I in scleroderma sera. J Clin Invest. 1987;79:65-72 2. Kuwana M, Kaburaki J, Mimori T, Tojo T, Homma M. Autoantibody reactive with three classes of RNA polymerases in sera from patients with systemic sclerosis. J Clin Invest. 1993;91:1399-404 3. Fritzler MJ, von Muhlen CA, Toffoli SM, Staub HL, Laxer RM. Autoantibodies to the nucleolar organizer antigen NOR-90 in children with systemic rheumatic diseases. J Rheumatol. 1995;22:521-4 4. Fujii T, Mimori T, Akizuki M. Detection of autoantibodies to nucleolar transcription factor NOR 90/hUBF in sera of patients with rheumatic diseases, by recombinant autoantigen-based assays. Arthritis Rheum. 1996;39:1313-8 5. Imai H, Ochs RL, Kiyosawa K, Furuta S, Nakamura RM, Tan EM. Nucleolar antigens and autoantibodies in hepatocellular carcinoma and other malignancies. Am J Pathol. 1992;140:859-70 6. Lin W, Jia C, Yin H, Lu L. Clinical significance of the anti-Nucleolar Organizer Region 90 antibodies (NOR90) in systemic sclerosis. Eur J Intern Med. 2025;131:159-61 7. Dima A, Vonk MC, Garaiman A, Kersten BE, Becvar R, Tomcik M, Hoffmann-Vold AM, Castellvi I, et al. Clinical significance of the anti-Nucleolar Organizer Region 90 antibodies (NOR90) in systemic sclerosis: Analysis of the European Scleroderma Trials and Research (EUSTAR) cohort and a systematic literature review. Eur J Intern Med. 2024;125:104-10 8. Duffau P, Dimicoli S, Gensous N, Truchetet ME, Bordes C. Anti-NOR90 antibody associated with paraneoplastic systemic sclerosis. Clin Exp Rheumatol. 2022;40:2002-3 9. Yamashita Y, Yamano Y, Muro Y, Ogawa-Momohara M, Takeichi T, Kondoh Y, Akiyama M. Clinical significance of anti-NOR90 antibodies in systemic sclerosis and idiopathic interstitial pneumonia. Rheumatology (Oxford). 2022;61:1709-16 10. Parker JC, Burlingame RW, Webb TT, Bunn CC. Anti-RNA polymerase III antibodies in patients with systemic sclerosis detected by indirect immunofluorescence and ELISA. Rheumatology (Oxford). 2008;47:976-9 |
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