Small cell lung cancer tied to LEMS found too late for older patient
Man's case highlights urgent need to 'raise clinical awareness of LEMS'
A case of Lambert-Eaton myasthenic syndrome (LEMS) was identified in an older man who was initially hospitalized with a wrongful diagnosis of aspiration pneumonia.
He was later diagnosed with small cell lung cancer (SCLC), an aggressive form of lung cancer that is often associated with LEMS, but was too weak to undergo treatment.
“This case is a key reminder of the importance of a complete clinical approach. It is essential to raise clinical awareness of LEMS, a rare medical condition,” the scientists wrote.
The report, “Paraneoplastic Lambert-Eaton myasthenic syndrome: a diagnostic challenge,” was published in the journal BMJ Case Reports.
LEMS often linked with small cell lung cancer or other underlying cancer
LEMS is rare autoimmune disorder characterized by the production of self-reactive antibodies, also called autoantibodies, against voltage-gated calcium channels (VGCC). These protein channels are found at the neuromuscular junction — the site where nerve cells meet and communicate with muscle cells — and are key for nerve-muscle communication.
As a result, patients exhibit disease symptoms like muscle weakness, reduced tendon reflexes, and problems in the autonomic nervous system, which controls involuntary functions such as heart rate.
While LEMS can occur spontaneously, in up to 60% of cases it is associated with an underlying cancer, most often SCLC. This is because VGCCs are also present at the surface of some cancer cells. As such, the antibodies produced by the immune system to fight off cancer may impair nerve-muscle communication and lead to the onset of LEMS.
Clinicians in Portugal reported the case of a LEMS patient who was initially misdiagnosed with aspiration pneumonia, which occurs when food or liquid is inhaled into the airways or the lungs.
The man, who was in his 70s, was admitted to the hospital after choking while eating.
His clinical history included two months of depression and anxiety, and he was a heavy smoker. In the previous year, he had been hospitalized due to a brief psychotic episode.
In the year prior to his recent hospitalization, he experienced progressive and constant muscle weakness in the lower legs. Difficulties swallowing liquids and solid food, along with speech impairments and constipation, developed in the preceding months. No cognitive impairments or other psychiatric symptoms were seen.
An examination found diminished pulmonary sounds and blood oxygen levels that were below normal. Additionally, he had ptosis, a condition where the upper eyelid droops over the eye, a weak soft palate, weakness in the arms and legs, and poorer or absent reflex responses.
His larynx (voice box) was impaired due to problems in the autonomic nervous system. However, a brain CT scan revealed no lesions. At this point, he was diagnosed with aspiration pneumonia.
Electromyography — a test that measures electrical signals coming from muscles in response to nerve signals — detected anomalies in nerve-muscle communication that are consistent with LEMS. The diagnosis was confirmed by the presence of antibodies against VGCCs.
A CT chest scan revealed a nodule in his right lower lung. A PET scan suggested the presence of cancer metastases (spreading) to hilar lymph nodes, which are found in a particular region of the lung. He also tested positive for antibodies that serve as SCLC markers, including anti-SOX-1 and anti-CV2/ CRMP5.
Man responded to intravenous immunoglobulin therapy, but later had to stop it
The patient was diagnosed with cancer-associated LEMS. Lung biopsies using a guided-ultrasound technique came back negative for malignant cells.
After a discussion involving several physicians, and because a further biopsy was excluded due to his poor overall condition, a decision was made to not initiate cancer treatments and maintain close monitoring instead.
The patient was given intravenous immunoglobulin therapy, along with prednisone and pyridostigmine, with satisfactory results.
His difficulty in swallowing and speech impairments eased, and he regained the ability to walk.
The patient was discharged, but one month later was diagnosed with pulmonary thromboembolism, which occurs when a blood clot gets stuck in an artery in the lung, blocking blood flow to that area. It was linked to intravenous immunoglobulin therapy.
He started treatment to prevent blood clots and stopped the immunoglobulin therapy. In the following months, he was readmitted to the hospital several times due to pneumonia and a kidney infection.
His neurological symptoms were gradually worsening, with severe functional decline.
Six months later, a follow-up CT scan showed another mass in the lungs. A biopsy now confirmed SCLC and its spread.
“Due to his frailty, cancer treatment was not started. The patient died about a year after the LEMS diagnosis,” the scientists wrote.
Overall, “this clinical report illustrates unique LEMS diagnosis circumstances,” they wrote. “Clinical awareness is crucial to diagnose LEMS and urge cancer screening and early treatment.”