Patients treated with interferon alfa can develop autoantibodies and a
utoimmune diseases. We describe two patients who developed myasthenia
gravis with abnormal levels of serum anti-acetylcholine receptor antib
odies during interferon alfa-2b treatment for malignancies. One of the
se patients had myopathic findings on EMG and focal deficiency of cyto
chrome c oxidase on muscle biopsy.