Difficultés autour d’un syndrome de Lambert-Eaton

Lambert-Eaton Myasthenic Syndrome Recurrence Induced by Pembrolizumab in a Patient with Non-small-cell Lung Cancer

A 73-year-old woman in complete remission from localized small-cell lung cancer associated with Lambert-Eaton myasthenic syndrome (LEMS) 22 years earlier was referred to our hospital and diagnosed with non-small-cell lung cancer. After three courses of pembrolizumab, an immune checkpoint inhibitor, the patient complained of muscle weakness, fatigue, ptosis, and dysarthria. The anti-voltage-gated calcium channel antibody level was elevated, and waxing was observed on a high-frequency repetitive stimulation test using an electromyogram. We diagnosed her with recurrence of LEMS as an immune-related adverse event (irAE) induced by pembrolizumab. After intravenous immunoglobulin therapy, the patient's symptoms improved, and she was discharged.

Lambert-Eaton Myasthenic Syndrome Caused by Nivolumab in a Patient with Squamous Cell Lung Cancer

Lambert-Eaton myasthenic syndrome (LEMS) is a representative paraneoplastic neurological syndrome. Recently, nivolumab, an anti-programmed cell death 1 inhibitor, has been approved for advanced non-small-cell lung cancer. Careful attention should be paid to immune-related adverse events (irAEs), including neurotoxicity. We herein report a 73-year-old woman with LEMS that occurred during nivolumab treatment for pulmonary squamous cell carcinoma. After the 20th week of nivolumab, she experienced various neurological symptoms such as ptosis, lower limb weakness, and photophobia. Findings from a nerve conduction study and a positive anti-P/Q-type voltage-gated calcium channel antibody made a diagnosis of LEMS. Pyridostigmine and 3,4-diaminopyridine temporarily improved her symptoms. This was the first case of LEMS as a neurological irAE. LEMS should be considered as a possible neurological irAE.

[Lambert-Eaton myasthenic syndrome associated with pulmonary squamous cell carcinoma and circulating anti-P/Q-type voltage-gated calcium channel antibody]

We report a 64-year-old man diagnosed with Lambert-Eaton myasthenic syndrome (LEMS) associated with pulmonary squamous cell carcinoma. Circulating anti-P/Q-type voltage-gated calcium channel (VGCC) antibody was detected, and the patient was treated with 3,4-diaminopyridine. At age 61, chest radiograph revealed a tumor shadow in the right upper lung field. This was surgically removed, and a histological diagnosis of moderately differentiated pulmonary squamous cell carcinoma was obtained. After about 1 year, mediastinal metastasis was detected and 5-FU was administered. Eight months later, metastasis was noted in the left frontal hemisphere, and radiosurgical therapy was performed. The brain tumor gradually shrank but generalized fatigue, thirst, and gait disturbance developed after 4 months. A diagnosis of LEMS was made on the basis of neurological findings including proximal muscle weakness and absent tendon reflexes; autonomic symptoms (thirst, constipation, and impotence); characteristic electromyographic findings; and circulating anti-P/Q-type VGCC antibody. He has been treated with 3,4-diaminopyridine at a dose of 30 mg/day, resulting in marked improvement in symptoms but little change in electromyographic findings. The present case is very rare and suggests that anti-P/Q-type VGCC antibody may be involved in the mechanism of LEMS associated with pulmonary squamous cell carcinoma.

Distinct evolution of calcium channel antibody types in Lambert-Eaton myasthenic syndrome

To determine whether titers of anti-P/Q type and anti-N type calcium channel antibodies provide distinct information, both types of assay were performed during follow-up of 7 patients with Lambert-Eaton myasthenic syndrome (LEMS). In 4 patients with both antibody responses, titers evolved independently and often in an inverse relationship. Two patients with squamous cell lung carcinoma (SqCLC) produced anti-N type channel antibodies, but no detectable anti-P/Q channel responses. These results suggest that anti-N channel autoantibodies constitute an immune response distinct from the anti-P/Q type channel specificity and can also correlate with clinical evolution. Consequently combined assays may provide more comprehensive information during follow-up of LEMS.