ANTIMITOCHONDRIAL (PYRUVATE-DEHYDROGENASE) AUTOANTIBODIES IN AUTOIMMUNE RHEUMATIC DISEASES

Anti-pyruvate dehydrogenase (PDH) antibodies were determined in 1451 sera of patients with primary biliary cirrhosis (PBC) and several autoimmune rheumatic conditions by ELISA and immunoblotting. They were detected in sera of 93% of the patients with PBC (179 of 192 patients) in 60 of 277 (22%) patients with Sjogren's syndrome (SjS), 34 of 437 (8%) patients with scleroderma, 33 of 191 patients with SLE (17%), and 5 of 55 (10%) patients with rheumatoid arthritis (RA) but in none of the patients with polymyositis or the antiphospholipid syndrome. The ELISA studies were confirmed by immunoblots showing binding of autoimmune rheumatic sera to the same epitope (74 kd) of mitochondria that the PBC sera reacted with. The identical binding characteristics were also confirmed by protein competition assays with purified PDH. In 4 of 53 patients with SjS who were positive for anti-PDH, high titers as in PBC were detected. The anti-PDH antibodies in Sjogren's patients were associated with deranged liver function tests and extraglandular features but did not correlate with any other non-organ-specific antibody. Follow-up studies confirmed the association of the emergence of anti-PDH antibodies with defects in liver function tests. The antibodies were more prevalent in SLE and RA when they were associated with Sjogren's syndrome (30 and 18.8%, respectively). Among patients with different forms of scleroderma, anti-PDH antibodies were noted in subjects with systemic sclerosis, morphea, and Raynaud's phenomenon. The incidence was much more significant among patients with calcinosis, Raynaud's, esophageal dysmotility, sclerosis, and telangiectasia (CREST) (8/34), in whom antibodies were detected in 5 who had already developed PBC. The relationship among anti-PDH antibodies, PBC, and development of other autoimmune rheumatic conditions is discussed. It is proposed that the early detection of anti-PDH antibodies in patients with rheumatic conditions may predict the future development of PBC. This observation may have therapeutic implications.