Abstract
A 13-month-old spayed toy poodle, weighing 3.85 kg, was brought to us with a history of gradually progressive trismus and difficulty in eating. Although physical examinations revealed that the dog’s general condition was good, and that there were no abnormalities around the temporomandibular joints, atrophy of the temporal and masseter muscles was palpated, and resistance to opening of the mouth was recognized. Routine blood tests detected mild leukocytosis and marked elevation of C-reactive protein value (12 mg/dl). From these clinical findings, we suspected autoimmune inflammatory muscle disorders. Type 2M myofiber antibody was measured, which resulted in striking increase of the antibody titers, that is, above 1:4000 (reference titer<1:100). Therefore the disease was diagnosed as masticatory myositis. Prednisolon (2 mg/kg/day) was prescribed, and the trismus was improved on the 7 th day. The drug was diminished gradually, and the therapy was stopped 138 days after the first presentation because there was no recurrence of the trismus. Four months later, however, the disease recurred, and treatment was resumed.
