A 68‐year‐old woman presented to our hospital with worsening orthopnea 3 times during 1 month. On her first hospitalization, she was diagnosed with diastolic heart failure in the setting of a normal B‐type natriuretic peptide (BNP) and echocardiogram. Shortly after discharge she developed sudden‐onset dysarthria which resolved over several hours. The subsequent re‐admission for workup of transient ischemic attack was unremarkable. Another dysarthric episode within 24 hours of her second discharge prompted her third hospitalization within 3 weeks. On evaluation, she was breathing comfortably and spoke in full sentences without notable dysarthria. However, her daughter stated that her speech had been slightly slurred for weeks. She complained of “head heaviness.” She denied ptosis, diplopia, difficulty masticating, dysphagia, proximal muscle weakness, or variability in symptoms with time of day. Oxygen saturation was 93% on 2 L sitting and 82% supine. Pulmonary function testing showed a restrictive pattern (forced vital capacity [FVC] of 1.32, 41% of predicted). An afternoon negative inspiratory force was approximately −10 cm H2O. CT scan of the chest revealed a new right middle lobe aspiration pneumonia. Within several days, the patient developed progressive neck extensor, oculobulbar and shoulder girdle weakness, and fatigability. Cervical spine MRI was negative. She developed profound difficulty with mastication. Evening 60‐second upgaze elicited ptosis. EMG showed increased jitter and antiacetylcholine receptor antibodies were positive. The patient was started on prednisone, pyridostigmine, and underwent plasmapheresis. In the 5 months since diagnosis with myasthenia gravis, she has been stable on azathioprine and prednisone and has not had any subsequent hospitalizations.
Myasthenia gravis is an autoimmune disorder of transmission at the neuromuscular junction. Although myasthenia classically presents with weakness in proximal and oculobulbar muscles that is progressive throughout the day, discrete exacerbations with fatigue or emotional stress are well documented. Patients rarely present with diaphragmatic weakness; in one series only 14% of myasthenics in respiratory failure were undiagnosed prior to hospitalization. Aspiration pneumonia is the most common cause of myasthenic crisis. It is likely that myasthenic dysphagia caused the patient's aspiration pneumonia, which led to her rapid deterioration after a long period of indolence.
Initial presentation of myasthenia gravis can be variable. Aspiration pneumonia is an uncommon presentation of myasthenia gravis, but it is the most common trigger of myasthenic crisis.
To cite this abstract:Bouffard M, Gromski M, Farris G. A Weak Diagnosis: Myasthenia Gravis Presenting with Severe Orthopnea. Abstract published at Hospital Medicine 2013, May 16-19, National Harbor, Md. Abstract 356. Journal of Hospital Medicine. 2013; 8 (suppl 2). https://www.shmabstracts.com/abstract/a-weak-diagnosis-myasthenia-gravis-presenting-with-severe-orthopnea/. Accessed April 10, 2020.