Acute familial myositis with a common autoimmune response

In 1986, we diagnosed and treated 4 patients, all members of 1 rural family, who presented simultaneously with a polymyositis-like syndrome, anticytoplasmic antibodies (on HEp-2 cells), and precipitating antibodies of anti-Jo-1 and anti-PM-Scl specificities. Serum samples from these patients reacted by immunodiffusion against serum from a rodent that had been caught in the patients' house. The precipitin line showed complete immunologic identity with anti-Jo-1. To study the specificity of this serum-serum reaction, 2 mice (Mus musculus) and 1 rat (Rattus rattus) from the neighboring areas of the patients' house were caught and killed. Sections of the liver, kidney, spleen, and skeletal muscle were processed for histopathologic examination and for direct and indirect immunofluorescence studies of the patients' sera. The rodents' sera were tested by immunodiffusion against serum samples from 25 patients with systemic lupus erythematosus, 11 with rheumatoid arthritis, 6 with mixed connective tissue disease, and 11 with various other rheumatic diseases, as well as 16 healthy controls. A serum-serum precipitin reaction was noted between the rodents' sera and sera from 2 of the patients with polymyositis-like syndrome. A distinct, but weaker, reaction was found with 2 lupus patients' sera (8%), and with 1 healthy control serum (6%). The rodents' sera were antinuclear antibody positive by indirect immunofluorescence on HEp-2 cells. These results, suggest that some rodents could be carriers of an as-yet-unknown transmissible agent that, in susceptible individuals, induces clinical and serologic manifestations similar to those of polymyositis.