Clinical Significance of Antinucleolar Antibodies: Biomarkers for Autoimmune Diseases, Malignancies, and others.

Nucleolar staining is one of the standard patterns in immunofluorescence antinuclear antibodies (ANA), seen in 5-9% of ANA in various conditions. Antinucleolar antibodies (ANoA) are classified into 3 patterns in the International Consensus on ANA Patterns (ICAP) classification; AC-8 homogeneous pattern, AC-9 clumpy pattern, and AC-10 punctate pattern. Specificities known to show AC-8 include anti-Th/To, -PM-Scl, -nucleophosmin/B23, -nucleolin/C23, -No55, and others. AC-9 is seen by anti-fibrillarin/U3RNP and AC-10 by anti-RNA polymerase I and hUBF/NOR-90. ANoA has been classically known to be associated with scleroderma (SSc) and the characterization of nucleolar antigens identified several autoantigens recognized by SSc autoantibodies. The clinical association of anti-Th/To, PM-Scl, fibrillarin/U3RNP, and RNA polymerase I with SSc or SSc-overlap syndrome is well established, and commercial assays are developed. Anti-hUBF/NOR90, nucleophosmin/B23, and nucleolin/C23 are known for decades and reported in systemic autoimmune rheumatic diseases (SARDs), malignancies, graft versus host disease (GVHD), and others; however, their clinical significance remains to be established.