Acquired myasthenia gravis (MG) is an autoimmune disease in which antibodies against the nicotinic acetylcholine receptor (AChR) at the neuromuscular junction cause weakness that gets worse with activity. In dogs it is probably the most common neuromuscular disorder that can be both diagnosed and treated (Shelton 2002), and it is a classic hidden cause of adult-onset megaesophagus. Most deaths come from aspiration pneumonia, not from the weakness itself.
Key facts
Myasthenia gravis at a glance- Species and system: dog; nervous system, neuromuscular junction (postsynaptic).
- Cause: autoantibodies against the muscle nicotinic AChR; sometimes paraneoplastic with a thymoma. Rare congenital myasthenic syndromes are inherited and antibody-negative.
- Classic dog: adult dog with regurgitation from megaesophagus, exercise-induced weakness that improves with rest, and a palpebral reflex that fades when repeated.
- Diagnosis: serum AChR antibody titer by immunoprecipitation radioimmunoassay; >0.6 nmol/L is diagnostic in dogs.
- Treatment: pyridostigmine, upright feeding and early treatment of aspiration pneumonia; thymectomy for thymoma.
- Outcome: spontaneous remission is common in dogs that survive, but 1-year mortality across all forms is 40–60%.
- Not zoonotic and not reportable.
What's inside
11 sections in the full guide- Key facts
- How the NAVLE tests this
- Cause and pathophysiology
- Clinical signs
- Diagnosis
- Differential diagnoses
- Treatment and management
- Prognosis
- Quick review
- Test yourself
- References
The full guide also has 5 tables, 3 figures, 3 self-test questions and 19 references, available to NAVLE members.
Read the full study guide
The full guide is part of every NAVLE plan, with diagnosis and treatment tables, figures, a quick review and self-test questions. Start a free trial to try the question bank, or log in if you are already a member.