Researchers have now reported a rare case of LEMS associated with two types of cancer in a patient: breast cancer and small cell cancer of the cervix.
The case was reported by researchers at Shizuoka Cancer Center Hospital in Japan.
Their study, “Lambert-Eaton Myasthenic Syndrome Associated with Synchronous Double Cancer: A Combination of Small Cell Carcinoma of the Cervix and Breast Carcinoma,” was published in the journal Internal Medicine.
LEMS is an autoimmune disorder caused by the disruption of communication between nerve cells and muscles. This is due to the overproduction and accumulation of antibodies that block nerve cells’ electrical signals, preventing muscles cells from receiving them.
The patient, a 64-year-old woman, had been treated for breast cancer and underwent a mastectomy of the affected breast. Two months later, she complained of general fatigue, leg weakness, and weight loss. She also noticed that her arms became tired very easily, and she had dry mouth.
To find the source of the symptoms, the clinical team conducted computed tomography (CT) scans, which revealed abnormal masses in her pelvis and metastasis in her lymph nodes. Additional examinations confirmed she had small cell cervix cancer, which was not a recurrence of her previous breast cancer.
“The advanced state (Stage 3b) of the [cervix cancer] was thought to be the cause of her serious condition, as small cell carcinoma of the cervix frequently shows an aggressive progression,” researchers wrote.
She was treated for a month with combined radiotherapy and chemotherapy. This promoted slight improvements to her unsteady gait, but the remaining symptoms persisted with variable severity.
After five months of persistent muscle weakness, the patient was examined by a neurologist. No significant damage to her cranial nerves was detected, and she also showed normal strength in her arms. But she had marked weakness of hip flexion and mild weakness in her knee extension.
Nerve cell electrical conductance studies revealed low electrical potential in the right feet, and repetitive nerve stimulation testing confirmed nerve electrical impulse abnormalities.
Based on these findings, the team evaluated the levels of calcium channel blocking antibodies. These were found to be approximately 4.9 times higher than the normal upper limit, which confirmed the diagnosis of LEMS.
She was treated with intravenous gammaglobulin for five days, followed by Mestinon (pyridostigmine). This improved her symptoms and enabled her to climb stairs without assistance.
Despite the improved symptoms and continued chemotherapy for her cervix cancer, the woman died a year after LEMS onset due to cancer metastasis.
The researchers believe this case highlights the importance of considering a diagnosis of LEMS in cancer cases that also present leg weakness.
“A systemic survey of malignant tumors, including gynecological carcinoma as well as lung small cell carcinoma, should be performed for LEMS patients,” they wrote. “The accurate diagnosis and urgent treatment of such carcinomas are important.”