Clinical features of 39 patients with antibodies to extractable nuclear antigens despite negative antinuclear antibodies: evidence for autoimmunity including neurologic and connective tissue diseases.

Systemic lupus erythematosus (SLE) rarely presents with a negative antinuclear antibody (ANA). Although antibodies to extractable nuclear antigens (ENA) are sometimes ordered despite a negative ANA, it is unclear if this contributes to the diagnosis of SLE or other forms of connective tissue disease (CTD). We reviewed 39 patients with anti-ENA antibodies despite a negative ANA during a 1-year period to determine the presence of SLE or other CTD. Several patients had clinical features suggestive of CTD, including 1 with possible SLE. A number of patients had neurologic disorders, especially peripheral neuropathy. In this study, the finding of anti-ENA despite negative ANA was associated with neurologic disorders and CTD. This may represent test bias or false-positive anti-ENA assays or false-negative ANA assays, or may imply immune-related mechanisms not previously described.