To describe a short series of patients (n = 5) carrying a clinical diagnosis of myasthenia gravis, who then developed neurological symptoms, that were initially attributed to myasthenia gravis, but later led to the diagnosis of a secondary neurological condition.

Patients with myasthenia gravis often present with myriad of neurological symptoms (e.g.double vision, weakness, fatigue).  On occasion, these symptoms may be falsely attributed to myasthenia gravis, when, in fact, the patient has developed an alternative neurological diagnosis.

A descriptive study of 5 patients (case-series).

We describe 5 patients with myasthenia gravis who have later developed concomitant neurological diseases:  (1) A 69-year-old woman who developed diplopia and ptosis due to an ischemic third nerve palsy.  (2) A 68-year-old woman who developed foot drop due to lumbosacral radiculopathy.  (3) A 72-year-old man who developed arm weakness due to amyotrophic lateral sclerosis.  (4) An 83-year-old man who developed leg weakness due to post-polio syndrome.  (5) A 37-year-old woman who developed daytime fatigue due underlying sleep disorder.

Patients with myasthenia gravis may develop other neurological disorders leading to weakness. If the diagnosis is not made accurately, patients may be exposed to procedures and treatments they may not need, which may even cause potential harm.  Certain characteristics of myasthenia gravis, or its treatment, may, in fact, predispose patients to developing these conditions.  The physician must maintain a high clinical suspicion for other neurological disorders, particularly when the patient’s symptoms or physical examination findings are not consistent with what would be expected from myasthenia gravis.