LEMS diagnosed in woman with other autoimmune conditions
She had previously been seen to have NMOSD, thyrotoxicosis
A 56-year-old woman was diagnosed with Lambert-Eaton myasthenic syndrome (LEMS) after having been earlier diagnosed with other autoimmune conditions, a U.K. case study reports.
The woman’s previous conditions included neuromyelitis optica spectrum disorder (NMOSD), which primarily affects the spinal cord and optic nerve, which sends and receives signals from the eyes, and autoimmune thyrotoxicosis, a condition marked by excessive thyroid hormones.
“LEMS is associated with additional autoimmune diseases in about half of cases. This case illustrates the importance of recognizing other treatable autoimmune conditions in the context of NMOSD,” the researchers wrote in the study, “Multiple autoimmunity: neuromyelitis optica spectrum disorder with Lambert-Eaton myasthenic syndrome,” which was published in Practical Neurology.
LEMS is a rare disease caused by the immune system attacking a specific type of calcium channel at nerve cell endings, called voltage-gated calcium channels (VGCCs). These are needed for the release of acetylcholine, a chemical messenger that triggers muscle contraction, playing a key role in controlling muscle movement.
Reaching a diagnosis of LEMS
The woman was first seen with a six-month history of declining mobility that included balance issues, difficulty walking, and fatigue. She also said her speech had deteriorated, and she’d had a hoarse voice and difficulty swallowing solid food in the last two months, along with ongoing visual blurring.
She’d been diagnosed with NMOSD two years before, after an episode of optic neuritis (optic nerve inflammation), and she’d had a second episode eight months before going to the hospital. Her medical history also included thyrotoxicosis of autoimmune origin, high blood pressure, and high cholesterol. She oman was a long-term smoker.
When she was first seen, she was taking the immunosuppressant azathioprine, along with medications to control her blood pressure and cholesterol. She was also on thyroid hormone replacement therapy. She had normal vision and eye reaction to light, impaired walking due to poor balance, and clinically normal function of the muscles and nerves in the head, neck, and throat. Her deep tendon reflexes were absent, and she had no sensory deficits.
Lab tests showed thyroid function abnormalities, low lymphocyte (immune cell) counts, and aquaporin-4 (AQ4) antibodies, which are related to NMOSD. Nerve conduction studies showed normal sensory responses, but severely attenuated motor responses from both the arms and the legs, which were changed after brief exercise. This indicated she had a condition that affected muscle-nerve communication, likely LEMS. A diagnosis was confirmed in further tests that showed the presence of antibodies targeting VGCCs in the blood. CT scans revealed no underlying cancer, which is often associated with LEMS.
“Even suspected autoimmune cases of LEMS require surveillance for an underlying neoplasm; this patient’s chronic smoking history, insidious weight loss, and hoarse voice made [cancer-associated] LEMS the initial suspicion,” the researchers wrote.
The woman continued taking azathioprine and started amifampridine, which is sold as Firdapse, followed by a five-day course of intravenous immunoglobulin (IVIG) due to her persistent severe symptoms. The treatment led to a marked improvement in tolerating exercise.
While treatment eased her symptoms in the long term, she started having breakthrough symptoms and started rituximab at six monthly intervals. At her last follow-up, the woman’s ability to swallow had been fully restored. She also regained her lost weight and was able to return to her full-time job. Her NMOSD has remained in remission, even though she continued testing positive for AQP4 antibodies.
The case “illustrates the importance of considering additional, treatable autoimmune diseases in neuromyelitis optica spectrum disorder patients presenting with new or persistent neurological symptoms,” the researchers wrote.
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