Lambert-Eaton myasthenic syndrome against the background of thyroid cancer: a clinical case

BACKGROUND: Lambert-Eaton myasthenic syndrome (G73.1 according to ICD-10) is a rare autoimmune disease associated with a presynaptic impairment of neuromuscular transmission due to the production of antibodies to voltage-gated calcium channels. The peculiarity of Lambert-Eaton myasthenic syndrome is manifested in a combination of increased muscle weakness and fatigue with the phenomenon of «working in» - an increase in the muscle strength against the background of muscle load after a short-term maximum contraction. Lambert-Eaton myasthenic syndrome is often associated with small cell lung cancer and very rarely develops with tumors of another localization. CLINICAL CASE DESCRIPTION: We observed an 80-year-old patient with complaints of weakness and pain in the hips, shoulders, pelvic region, and half-ptosis of the eyelids. For half-ptosis of the eyelids, a differential diagnosis was conducted with myasthenia gravis. Stimulation electromyography revealed the M-response increment, i.e. the phenomenon of “working in”, which is typical for this syndrome. The examination revealed papillary thyroid cancer, which was later treated surgically.