AB0163 ANTI-KU ANTIBODIES: MUCH MORE THAN SCLEROMYOSITIS
Authors: L. Montolio-Chiva, J. Narváez, F. Morandeira, J. Bas, C. Marco, X. González, J. J. Alegre-Sancho, E. Flores, I. Vázquez-Gómez, J. M. López, J. M. Nolla
Journal: Annals of the Rheumatic Diseases (2020)

Background: Initially, anti-Ku antibodies (Ab) were described in patients with overlap syndrome with systemic sclerosis (SSc) and inflammatory myophaty (scleromyositis), although later they have been linked to a wide variety of systemic autoimmune diseases (SAD) questioning its diagnostic value. Recently, the possible existence of 2 different clinical phenotypes associated with these Ab has been described: one with myositis and high risk of intersticial lung disease (ILD) and another with positive anti-dsDNA Ab and glomerulonephritis. Objectives: To analyze the clinical relevance and the main diagnosis of a serie of patients with positive anti-Ku Ab. Methods: Descriptive observational study of patients with anti-Ku Ab in two third level hospitals between 2011 and 2019. Their determination was made at the criteria of the requesting physician. Results: Twenty-three patients (20 women) with a median age of 59 ± 14 years (range, 24-83) and a follow up time (median) of 37 months (1-208) were identified. The main clinical and analytical characteristics, as well as the final clinical diagnosis of these patients are shown in Table 1. In the cluster analysis we could not identify clinical phenotypes, perhaps because of the small sample size. Only 50% of patients with myositis developed ILD. Regarding the final diagnosis, only 1 patient (5%) was diagnosed of scleromyositis. Besides detecting them in patients with SSc (39%) and idiopathic inflammatory myopathy (9%), anti-Ku Ab were detected in other SAD, the most frequent were systemic lupus erythematosus, rheumatoid arthritis (RA) and overlap syndrome of SSc + RA. Table 1. Main clinical-analytical manifestations and final diagnosis of pacientes with anti-Ku Ab. FINAL CLINICAL DIAGNOSiS Scleromyositis: 1 Idiopahtic inflammatory myopathy: 1 Systemic sclerosis (SSc): 6 (Pre-scleroderma: 3, limited SSc: 3). Systemic lupus erythematosus: 2 Rheumatoid arthritis: 2 Overlap syndrome RA + limited SSc: 2 Primary Sjögren’s syndrome: 1 (Secondary Sjögren’s syndrome: 3) Mixed connective tissue disease: 1 Polymyalgia rheumatica: 1 Undifferentiated connective tissue disease: 1 Acute hepatitis due to HEV: 1 Autoimmune thrombocytopenia (ITP): 1 Drug-induced fibrosing ILD: 1 Systemic graft versus host disease (GVHD) in a patient with acute lymphoblastic leukemia who received and autologous haematopoietic progenitor transplant: 1 Primary biliary cirrhosis: 1 CLINICAL MANIFESTATIONS (patients could have more than one): Raynaud’s phenomenon: 61% (14/23). Inflammatory arthralgia/arthritis: 52% (12). Lung involvement: 30.5% (7: NSIP 3, UIP 2, other patterns 2). Serositis: 26% (6: pericarditis 4, pleuritis 1, pleuropericarditis 1). Cardiac involvement: 26% (6: PHT by echocardiogram 3, myocarditis 2, arrhytmia 1). Dry syndrome: 17% (4) Myositis: 17% (4). Esophageal involvement: 17% (4). Autoimmune cytopenias: leucolinfopenia: 17% (4) / thrombocytopenia: 13% (3). Telangiectasias: 13% (3). Photosensitivity: 13% (3). Other: non-androgenic alopecia: 9% (2); sensory-motor polyneuropathy: 4.5% (1); Puffy hands : 4.5% (1); fever: 4.5% (1); lymphadenitis: 4.5% (1); cold sores: 4.5% (1), and retinal hemorrhage: 4.5% (1). OTHER ASSOCIATED ANTIBODIES: ANA: 91% (21/23) anti Ro60/SSA Ab: 30.5% (7) Anti Ro52 Ab: 30.5% (7) Anti RNP Ab: 22% (5) Anti-dsDNA: 17% (4) Anti-La/SSB Ab: 17% (4) Anticentromer Ab: 17% (4) Anti Mi-2 Ab: 13% (3) Other: anti Sm Ab: 9% (2); anticardiolipin Ab(IgG): 4.5% (1); PM/Scl: 4.5% (1); nucleosomes: 4.5% (1); Scl70: 4.5% (1); PL12: 4.5% (1); anti-U1-RNP: 4.5% (1) and NOR90: 4.5% (1). Conclusion: Anti-Ku Ab are related to a great variety of SAD, without being a specific marker of any of them, nor being associated with any specific clinical manifestation. We couldn’t confirm the existence of clinical phenotypes associated with the presence of these antibodies. Disclosure of Interests: L Montolio-Chiva: None declared, J. Narváez: None declared, Francisco Morandeira: None declared, Jordi Bas: None declared, Carla Marco: None declared, Xavier González: None declared, Juanjo J Alegre-Sancho Consultant of: UCB, Roche, Sanofi, Boehringer, Celltrion, Paid instructor for: GSK, Speakers bureau: MSD, GSK, Lilly, Sanofi, Roche, UCB, Actelion, Pfizer, Abbvie, Novartis, Eduardo Flores: None declared, I Vázquez-Gómez: None declared, Jose María López: None declared, Joan Miquel Nolla: None declared