Overlapping symptoms hide a pair of rare autoimmune diseases
Case of woman, 70, suggests dual diagnoses are overlooked, per report
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An older woman with Sjögren’s disease who developed problems walking was ultimately also diagnosed with Lambert-Eaton myasthenic syndrome (LEMS), revealing a rare coexistence between two autoimmune diseases that can share overlapping symptoms, according to a case report.
The researchers noted that the second diagnosis, made after nerve studies, likely took longer because the woman’s LEMS symptoms were “initially attributed solely to Sjögren’s,” leading to a “primary working diagnosis” that did not suggest other autoimmune diseases.
This “case represents only the third reported association between LEMS and Sjögren’s,” and the first “in a Caucasian individual,” the researchers noted.
But it raises the suspicion, the team suggests, that there are other cases like this woman’s in which people with LEMS may have other autoimmune diseases, including Sjögren’s. According to the researchers, the co-occurrence of the two conditions may be underdiagnosed.
A report detailing the woman’s diagnosis, titled “Lambert-Eaton myasthenic syndrome in association with Sjögren’s syndrome: a case report,” was published in the journal Acta Neurologica Belgica.
LEMS is an autoimmune neuromuscular disease in which self-reactive antibodies target proteins called voltage-gated calcium channels (VGCC), preventing nerve cells from properly sending signals to muscle cells.
This leads to the disease symptoms, such as muscle weakness, reduced reflexes, and autonomic dysfunction, or symptoms related to involuntary bodily processes such as the production of saliva and tears. Dry mouth and dry eyes, also known as sicca symptoms, affect about 90% of LEMS cases.
These are also the most common symptoms of Sjögren’s, an autoimmune disease that mainly affects moisture-producing glands.
Woman’s LEMS symptoms first attributed to Sjögren’s
Now, a team of researchers in Czech Republic described the case of a 70-year-old woman with Sjögren’s who developed LEMS.
The woman started experiencing trouble climbing stairs in May 2023, which eased with oral corticosteroids — anti-inflammatory and immunosuppressive medications. However, the problems returned after she discontinued the medications in January 2024.
A few months later, her motor problems started to worsen progressively, resulting in walking problems that required the use of a low walker, as well as arm weakness that prevented her from performing certain movements such as throwing. The woman also experienced general weakness and urinary infections, the report noted.
A clinical examination indicated that the woman had muscle weakness mainly affecting muscles closer to the trunk, particularly in the hips and pelvic region. This contributed to a waddling walking pattern, characterized by side-to-side hip movements, and difficulty standing up from a chair without assistance, the researchers noted.
She also had reduced or absent deep tendon reflexes, although some reflex responses temporarily improved after muscle activation. This is a characteristic feature of LEMS known as facilitation. An MRI of the thighs showed widespread muscle shrinkage.
Nerve conduction studies, which evaluate the ability and speed at which nerve cells send signals to muscles, showed low-amplitude compound muscle action potentials, or CMAP, indicating reduced muscle responses to nerve stimulation. After the woman exercised the muscle, CMAP amplitude increased, which is highly suggestive of LEMS.
Electromyography, which records electrical signals coming from muscles in response to nerve signals, and repetitive nerve stimulation testing confirmed a problem with nerve-muscle communication, also supporting a LEMS diagnosis.
That diagnosis was finally confirmed with the detection of elevated levels of anti-VGCC antibodies in the blood, according to the team.
The researchers reported that the woman also had symptoms that included dry mouth, which, the team noted, “are present in approximately 90% of LEMS cases.” However, these symptoms were first attributed only to the woman having Sjögren’s, according to the researchers.
The woman was also found to have self-reactive antibodies consistent with Sjögren’s.
Woman’s case is third reported with these 2 rare autoimmune diseases
Treatment in this case involved a combination of pyridostigmine and prednisone, a corticosteroid, alongside cyclic administration of intravenous immunoglobulin (IVIG) every 4-5 weeks, per the case report.
Pyridostigmine is approved under the brand name Mestinon (with generic versions available) to treat myasthenia gravis, another neuromuscular disease, and is sometimes used off-label to treat muscle weakness in LEMS. IVIG involves the administration of healthy antibodies to suppress antibody-induced autoimmune responses.
Following treatment, the woman experienced “significant clinical improvement,” regaining “the ability to walk independently,” the researchers wrote. Still, she continued to have a mildly waddling gait.
While LEMS is commonly associated with cancer, “repeated PET/CT scans of the trunk (the last one in 2026) showed no evidence of malignancy,” the researchers wrote, adding that “although most LEMS cases have a paraneoplastic [cancer] etiology [cause], there are instances of non-paraneoplastic LEMS associated with other autoimmune diseases.”
[This woman’s case] raises the hypothesis of whether Sjögren’s … in the context of LEMS might be underdiagnosed, as both conditions share overlapping autonomic symptoms.
According to the researchers, just two other cases of LEMS and Sjögren’s have been reported in the literature, and both occurred in Japanese people, indicating that this is the first case to be reported in a Caucasian person.
Overall, however, this woman’s dual diagnosis “raises the hypothesis of whether Sjögren’s … in the context of LEMS might be underdiagnosed, as both conditions share overlapping autonomic symptoms,” the team wrote.
The researchers noted that “further case reports and studies are needed to clarify this association.”
Linda Pyle
My husband was diagnosed with LEMS in 2018 and was diagnosed with sojourns in 2024.
Carol Ann Beatts
I was diagnosed with sero negative LEMS in 2024
I was diagnosed on symptomology and response to treatment
The symptoms for borh conditions quite similar
My symptoms have never subsided and are indeed now getting worse.
So its a case of living the best I can