28/09/2026
What approximate % of dogs with acquired myasthenia gravis have a concurrent megaoesophagus?
1. 25%
2. 45%
3. 65%
4. 85%
The answer is…. 85%
Myasthenia gravis is a condition affecting transmission at the neuromuscular junction and may either be acquired or congenital.
Acquired myasthenia gravis is an immune-mediated disorder with auto-antibodies directed against the neuromuscular junction of skeletal muscle, typically targeting the acetylcholine receptor, and preventing normal attachment of acetylcholine. It may be classed as focal (involving oesophageal, pharyngeal, laryngeal and/or facial muscles), generalised (with involvement of appendicular skeletal muscle) or acute fulminating (severe and rapidly progressive form presenting with tetraparesis/plegia and often respiratory compromise). The disease may also be considered thymoma or non-thymoma associated, or drug-induced (e.g. Methimazole use in cats).
It is often seen in large breed dogs where German Shepherds, Golden Retrievers, Labradors, German Short Haired Pointers and Akitas appear predisposed.
The most common clinical presentation is of generalised weakness and exercise intolerance with megaoesophagus. The latter is seen more commonly in dogs than cats due to the higher proportion of striated muscle rather than smooth in the oesophagus. Dogs may display paresis, a crouched posture and cervical ventroflexion, but return to normal with periods of rest. Additional regurgitation, dysphagia, dyspnoea, dysphonia and paresis of facial muscles may be evident. Spinal reflexes may be reduced or normal on examination, and it may be possible to see fatigue of the palpebral reflex with repeated stimulation. Respiratory distress due to aspiration pneumonia is a frequent complication, and the highest cause of mortality in dogs (approximately 40-60% at 1-year).
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