Lambert-Eaton myasthenic syndrome associated with thymic neuroendocrine carcinoma

Lambert-Eaton myasthenic syndrome

Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disease characterized by proximal muscle weakness, loss of tendon reflexes, and autonomic dysfunction. Muscle weakness usually starts in the upper legs and can progress to oculobulbar and in severe cases respiratory muscles. P/Q-type voltage-gated calcium channels (VGCCs) localized in the presynaptic motor nerve terminal and in the autonomic nervous system are targeted by antibodies in LEMS patients. These antibodies can be detected in about 90% of patients, and the presence of decrement and increment upon repetitive nerve stimulation is also a highly sensitive diagnostic test. Rapid diagnosis is important because of the association with SCLC in 50%-60% of patients, which stresses the need for vigorous tumor screening after diagnosis. Clinical parameters can predict tumor probability and guide frequency of tumor screening. Treatment of the tumor as well as symptomatic treatment and immunosuppression can effectively control symptoms in the majority of patients.

Presynaptic Paraneoplastic Disorders of the Neuromuscular Junction: An Update

The neuromuscular junction (NMJ) is the target of a variety of immune-mediated disorders, usually classified as presynaptic and postsynaptic, according to the site of the antigenic target and consequently of the neuromuscular transmission alteration. Although less common than the classical autoimmune postsynaptic myasthenia gravis, presynaptic disorders are important to recognize due to the frequent association with cancer. Lambert Eaton myasthenic syndrome is due to a presynaptic failure to release acetylcholine, caused by antibodies to the presynaptic voltage-gated calcium channels. Acquired neuromyotonia is a condition characterized by nerve hyperexcitability often due to the presence of antibodies against proteins associated with voltage-gated potassium channels. This review will focus on the recent developments in the autoimmune presynaptic disorders of the NMJ.

Thymic Small Cell Carcinoma Associated With Lambert-Eaton Myasthenic Syndrome

Thymic small cell cancer is a very rare type of thymic epithelial tumor. Lambert-Eaton myasthenic syndrome is a rare paraneoplastic syndrome associated with thymic epithelial tumors. We report an extremely rare case of Lambert-Eaton myasthenic syndrome associated with thymic small cell carcinoma. A 71-year-old man was referred to our institution for a mediastinal tumor and a 2-month history of ptosis, fatigue, and gait disorder. Based on radiologic findings thymoma associated with Lambert-Eaton myasthenic syndrome was diagnosed, and extended thymectomy was performed. After surgery the patient's symptoms had not improved. Anticholinesterase treatment alleviated his symptoms.