Unusual symptoms of LEMS seen in rare case of woman, 62: Report
Patient found to have respiratory failure, unresponsive pupils
A 62-year-old woman with a long history of smoking was diagnosed with Lambert-Eaton myasthenic syndrome (LEMS) after experiencing rare symptoms of the autoimmune disease — specifically, early respiratory failure and unresponsive pupils. These symptoms occurred following an in-hospital cardiac arrest, the clinicians noted in a case report.
Initially treated for shortness of breath at Canisius Wilhelmina Hospital, in the Netherlands, the woman was hospitalized two weeks later for suspected pneumonia, and then went into cardiac arrest the following day. A neurological examination showing her fixed pupils, along with a severe loss of muscle tone and weakness, led clinicians to suspect LEMS, despite the patient not meeting the typical diagnostic criteria.
“Developing severe respiratory failure is rare in LEMS,” the clinicians wrote, noting also that “sluggish pupillary reflexes are common but dilated fixed pupils are rare.”
Electrophysiological testing, done “six days after the first investigation,” ultimately led to a confirmation of the LEMS diagnosis, the clinicians noted.
The report, “Dilated fixed pupils and respiratory failure: a rare clinical course of Lambert-Eaton myasthenic syndrome,” was published in BMJ Neurology Open.
Patient initially believed to have Sjögren’s, not LEMS, due to symptoms
LEMS is an autoimmune neuromuscular disease in which self-reactive antibodies attack voltage-gated calcium channels that are important for nerve-muscle communication.
The disorder typically is diagnosed after a cardinal trio of LEMS symptoms are seen. One is weakness in the muscles closest to the core of the body, known as proximal muscle weakness, while another is reduced reflexes. The final element of the trio are autonomic symptoms, or symptoms related to involuntary bodily processes.
One autonomic function that can be affected is the pupillary reflex, when the eye’s pupil constricts in response to high light conditions or dilates in lower light conditions.
While it is fairly common in LEMS to see that these reflexes are sluggish — meaning the pupil is slow to respond to changes in light — it is rare for the pupil to be fixed in a dilated state and completely unresponsive.
Moreover, severe muscle weakness leading to respiratory failure is a possible, but uncommon disease manifestation.
Here, scientists described an unusual case of LEMS in which both of these symptoms were observed.
The patient first was evaluated by doctors for progressively worsening symptoms of dry mouth and eyes, and movement difficulties. While she had complained of shortness of breath, this was not found during the initial exam, and the woman had normal pupillary responses to light.
Lab tests returned as normal, and she was suspected of having Sjögren’s syndrome, an autoimmune disease affecting the the glands that make tears and saliva.
Still, the woman returned two weeks later with progressive breathlessness and was admitted to the hospital after an X-ray revealed signs of pneumonia.
The next day, the patient went into cardiac arrest due low oxygen levels, which was believed to be due to the fact that she was unable to cough up mucus in the respiratory tract. The mucus was suctioned out, and the woman still was was sedated and intubated with a breathing tube.
During a neurological exam, the woman’s pupils were wide, fixed, and mildly deformed in shape. She also had a loss of muscle tone and weakness in her arms and legs, as well as absent reflexes.
Together, these symptoms led the doctors to suspect LEMS, despite the fact that tests of nerve and muscle electrical function failed to meet the diagnostic criteria.
Patient’s LEMS symptoms eased, but then deteriorated
The woman was treated with daily oral Firdapse (amifampridine), an approved LEMS therapy, as well as intravenous immunoglobulin replacement therapy, an approach to help reset immune responses in people with autoimmune diseases.
Her muscle strength and pupils began to improve, but the woman still required a breathing tube. Additional nerve-muscle tests now revealed signs of LEMS, and she tested positive for antibodies against voltage-gated calcium channels.
Imaging tests also indicated the likely presence of small-cell lung cancer, a known cause of LEMS.
After about a month of continuous improvement, the woman’s muscle strength again deteriorated and additional treatments proved ineffective. The woman did not wish for additional diagnostic or therapeutic procedures and died after the breathing tube was removed.
The clinicians noted that people with LEMS may be particularly sensitive to neuromuscular blocking medications that are commonly used during medical procedures. While respiratory failure is rare in LEMS, it has been seen in patients treated with such neuromuscular blockers before it was known they had the disease.
In this case, the patient was given a neuromuscular blocker called rocuronium during breathing tube placement.
While it is possible that rocuronium could have contributed to her deterioration, the scientists don’t believe it is likely given that she only received a single dose.
Likewise, while long-term rocuronium has been associated with dilated fixed pupils, the short course she was given has not been linked to this symptom.
“Altogether, we deem it highly unlikely that the wide, fixated pupils could be attributed to the rocuronium (alone) and rather were a result autonomic dysfunction in the setting of LEMS,” the researchers wrote.
The scientists noted that the findings also highlight the importance of antibody testing, lung imaging, and nerve-muscle tests to support a LEMS diagnosis when clinical symptoms are observed.