Autoantibodies to Nuclear Lamin C in the Eosinophilia—Myalgia Syndrome Associated with L‐Tryptophan Ingestion

Objective. To examine the autoantibodies (antinuclear antibodies [ANA]) present in serum from a patient with eosinophilia—myalgia syndrome (EMS). Methods. Sera obtained during the early phase of EMS and following therapy with prednisone were screened by indirect immunofluorescence on HEp‐2 cells, and ANA were characterized by immunoblotting on a purified nuclear lamin fraction. Results. ANA with a ring‐like pattern of nuclear staining were identified at high titer by immunofluorescence, and immunoblotting experiments showed them to be directed against lamin C. The antibody titer declined dramatically after discontinuation of L‐tryptophan and therapy with prednisone. Conclusion. This is the first characterization of an antigen/autoantibody system associated with EMS. The findings indicate that this EMS‐associated autoantibody recognizes epitopes localized in the carboxyterminal region of lamin C. The occurrence of antilamin C autoantibodies in one EMS patient expands the spectrum of clinical conditions associated with these antibodies, and provides evidence for an autoimmune response in EMS.