A five-year old male castrated German Shepherd dog, presented to the Cornell University Hospital for Animals (CUHA) Emergency Service on September 11th, 2011 for hindlimb paresis and aspiration pneumonia. On initial assessment, the patient exhibited tetraparesis that worsened with activity. Repeat thoracic radiographs showed persistence of previously diagnosed megaesophagus and aspiration pneumonia. The patient was hospitalized and started on IV fluids and antibiotics and transferred to the Internal Medicine Service the next day. A Tensilon test was performed which was positive and treatment was initiated with pyridostigmine, dexamethasone, and mycophenolate mofetil for presumptive acquire myasthenia gravis. Anti-acetylcholine receptor antibody titers were submitted but the patient was deemed seronegative. Over the next 3 days, the patient improved and was discharged with near complete resolution of both the megesophagus and aspiration pneumonia. Using the above case as an example, the pathophysiology of acquired myasthenia gravis with a focus on diagnostic and treatment options will be discussed.