Background Anti-Ku antibody is a DNA-binding protein, initially described in the 80’s. Although, reported in a large variety of connective tissue diseases, they are a serologic marker of overlap syndromes, namely those that included myositis. The prevalence of antibodies against Ku protein is variable ranging from 2% to 55%. The discrepancy is due to the different detection methods, the disease type, the geographic clustering and the genetic background. In the meantime, several studies have been performed in order to assess the prevalence and the clinical significance of these antibodies in connective tissue diseases.
Objectives To describe clinical and serological associations of anti-Ku antibodies.
Methods Twelve patients with anti-Ku antibody detected by immunoblot were retrospectively evaluated.
Results Patients (7 women, 5men) had a mean age of 64.4 (range 29-83). Three had overlap syndromes: two polymyositis (PM)/scleroderma (SSc) and one arthritis rheumatoid (RA)/PM. Four additional patients had undifferentiated connective tissue disease, two RA, one PM, one SSc. Moreover, one patient had a monoclonal gammopathy. In the patients with connective tissue disease the clinical manifestations most frequently recorded were arthralgias (58%), myositis (42%) and Raynaud’s phenomenon (42%). Three patients had esophageal dysmotility, while 2 showed interstitial pulmonary fibrosis (one with reduced DLCO). One case of pulmonary hypertension was observed. The majority of the patients had favorable prognosis. Hence, 33% were not receiving treatment with immunosuppressors or immunomoduladors. Ongoing treatment included corticosteroids (40%), antimalaric drugs (30%), and methotrexate (20%). All patients had very high titer of ANA with speckled and nucleolar pattern. Three sera contained additional antibody specificities: anti-SSA, anti-Jo1 and anti-Pl7 in one each case.
Conclusions Anti-Ku antibody is reported in various connective tissue diseases including overlap syndromes and myositis. Raynaud’s phenomenon, muscular and joint involvement are the most frequent clinical manifestations associated with anti-Ku antibodies. Anti-Ku antibodies detection in myositis is associated with a favorable prognosis.
Disclosure of Interest None Declared