History. A 4-month-old, intact female German shepherd presented for inability to open the jaw. The owner reported an alteration in ear carriage 2 days before presentation. The puppy had also been lethargic and anorectic for approximately 24 hours. Routine vaccinations and deworming were up-to-date, and there was no history of previous illness, exposure to toxins, or interaction with other animals.

Examination. The patient was lethargic with a rectal temperature of 104° F. The heart and lungs were normal on auscultation, although the respiratory rate was elevated at 60 breaths/min. The jaw was unable to be opened, and ptyalism was profound. The ears and muscles of facial expression were severely contracted (Figure 1). The results of the remainder of the physical and neurologic examinations were within normal limits.

Ask Yourself ...

What is the most likely diagnosis for this 4-month-old puppy?A. Congenital myotoniaB. TetanusC. Chronic masticatory myositisD. Strychnine poisoningE. Temporomandibular disease

Correct Answer: B