Final answer:
Patients with Myasthenia Gravis may exhibit a facial appearance with muscle weakness, drooping eyelids, and a slack expression, due to the autoimmune disorder blocking acetylcholine receptors which affects neuromuscular function.
Step-by-step explanation:
The facial appearance of a patient with Myasthenia Gravis (MG) is characterized by muscle weakness, which can manifest as drooping eyelids and sometimes a slack facial expression. Because MG is an autoimmune disorder that blocks acetylcholine receptors at the neuromuscular junction, it causes symptoms like double or blurred vision, and in more advanced stages, may affect swallowing, breathing, and produce a symptom referred to as myasthenia crisis, where emergency medical care is required. An example of how the facial appearance changes can be seen in photographs before and after administering a drug that blocks the breakdown of acetylcholine, resulting in a temporary improvement of symptoms including the lifting of the drooping eyelids.