AUTOANTIBODIES TO A NUCLEOLAR RNA HELICASE PROTEIN IN PATIENTS WITH CONNECTIVE-TISSUE DISEASES

Objective. An autoantibody to a nucleolar RNA helicase protein (Gu) wa s recently discovered in a patient with gastric antral vascular ectasi a or watermelon stomach, a disorder that is increasingly being describ ed in systemic sclerosis (SSc), The present study was undertaken to de termine whether anti-Gu antibodies occur in connective tissue diseases (CTD) and, if so, to determine their frequencies and any clinical or immunogenetic associations. Methods. Anti-Gu antibodies were determine d by Western blotting of glutathione-purified glutathione S transferas e-Gu fusion proteins against consecutive antinucleolar antibody-positi ve sera (HEp-2 cell substrate) collected over a 5-year period in a rhe umatology antinuclear antibody (ANA) testing laboratory. Results. Anti -Gu antibodies were found in 11 (10%) of 108 antinucleolar antibody-po sitive sera, The subjects with anti-Gu antibodies included 3 of 46 pat ients with SSc (7%), 3 of 17 patients with systemic lupus erythematosu s (18%), 4 of 9 patients,vith undifferentiated CTD (44%), and 1 health y relative of an SSc patient, None of the anti-Gu-positive patients ha d any symptoms suggestive of watermelon stomach, Increased frequencies of both HLA-DQA10501* and DQB1*0301 were found, but only DQB1*0301 m aintained statistical significance after correction. Conclusion. Anti- Gu (nucleolar RNA helicase) antibodies occur in low frequencies in pat ients with CTDs who have antinucleolar antibodies by ANA testing, but they are not specific for SSc or the watermelon stomach lesion.