Autoimmunity in spontaneous myasthenia gravis in dogs.

Spontaneous canine myasthenia gravis (MG) mimics the human disease in almost every respect. Both dogs reported here exhibited the autoantibodies characteristic of MG, i.e., anti-acetylcholine receptor (anti-AChR) and antistriational (AStr). Fluctuations in the anti-AChR titer during spontaneous remission and recurrence of MG in one dog provide support for the concept of a symptomatic threshold titer above which anti-AChR must rise before disease signs develop. The increase in the anti-AChR titer and recurrence of disease signs followed vaccination and an infection. Interestingly AStr also reappeared in this dog and serum IgG concentration increased. AStr in the second dog was associated with the presence of a thymoma and had a staining pattern characteristic of human MG.