Prevalence and clinical associations of anti-Ku antibodies in systemic autoimmune diseases

Abstract

We retrospectively analysed the prevalence and clinical features associated to anti-Ku antibodies in patients affected by different autoimmune diseases. Anti-Ku antibodies are detected in 147 sera out of 7239 anti-ENA positive sera (2%). They are found in 2% of patients with systemic sclerosis (SSc) (8 out of 379), 1.8% of systemic lupus erythematosus (SLE) (7 out of 372) and 1.8% of undifferentiated connective tissue disease (UCTD) (9 out of 496) and more rarely in Sjögren Syndrome and rheumatoid arthritis. Most of anti-Ku positive patients were affected by UCTD and overlap syndromes, including polymyositis, SSc and SLE. Interstitial lung disease, myositis, articular symptoms, Raynaud's phenomenon and sicca represents the main clinical features detected in our cohort. The rate and severity of pulmonary disease is similar to those found in other SSc patients. Isolated anti-Ku were detected in about 47% of sera. No clinical differences were observed between these patients and subjects with multiple anti-nuclear specificities. However, anti-Ku are usually detected in association with other serological markers in SLE and Sjögren Syndrome, while they occurred isolated in SSc and polymyositis.

Single-specificity anti-Ku antibodies in an international cohort of 2140 systemic sclerosis subjects

“…The prevalence of anti-Ku autoantibodies in SSc varies from 1.5% to 16%, [13–25] depending primarily on the detection immunoassay, and on the genetic and geographical background of the subjects studied. [26] They were first described in 1981 by Mimori et al [19] as a marker of scleroderma-polymyositis overlap syndrome, but have since been reported in a variety of other autoimmune disorders, including systemic lupus erythematosus (SLE) (0.7%–27%), idiopathic inflammatory myopathies (up to 26%), mixed connective tissue disease and undifferentiated connective tissue disease (up to 8.3%), rheumatoid arthritis (up to 16%), and Sjögren syndrome (<1%–20%), in isolation or as part of overlap syndromes, [13,14,19,23–25,27–47] and only rarely in healthy controls.…”

“…[26] They were first described in 1981 by Mimori et al [19] as a marker of scleroderma-polymyositis overlap syndrome, but have since been reported in a variety of other autoimmune disorders, including systemic lupus erythematosus (SLE) (0.7%–27%), idiopathic inflammatory myopathies (up to 26%), mixed connective tissue disease and undifferentiated connective tissue disease (up to 8.3%), rheumatoid arthritis (up to 16%), and Sjögren syndrome (<1%–20%), in isolation or as part of overlap syndromes, [13,14,19,23–25,27–47] and only rarely in healthy controls. [19,23,25] In SSc, these autoantibodies have been associated with myositis [14,17,19,22,32,42,48] and ILD, [14,42] and also limited cutaneous involvement, [14,19,22] arthritis, [14,22] and less vascular involvement.…”

“…[19,23,25] In SSc, these autoantibodies have been associated with myositis [14,17,19,22,32,42,48] and ILD, [14,42] and also limited cutaneous involvement, [14,19,22] arthritis, [14,22] and less vascular involvement. [14,20–22] However, results have been conflicting, [13,22,24,25] and conclusions have been limited by small numbers of subjects studied and potentially confounded by the co-presence of other SSc-related autoantibodies.…”

Facial nerve palsy and anti-Ku autoantibodies

“…Autoantibodies against Ku are infrequently detected and found in high titers in patients with connective tissue diseases and overlap syndromes [2][3][4].…”

Sarcoid Myositis with Anti-Ku Antibody Consistent with both Sarcoidosis and Polymyositis

“…Subsequently, anti-Ku antibodies have been detected in various connective tissue diseases including systemic lupus erythematosus, Sjögren's syndrome and mixed connective tissue diseases (MCTD) (9,10). We herein report a rare case of sarcoid myositis with anti-Ku antibody positivity that strongly suggests the occurrence of both sarcoidosis and polymyositis.…”