Myasthenic syndrome of Lambert-Eaton on the background of thyroid cancer (clinical case)

Abstract

Lambert-Eaton myasthenic syndrome, G 73.1 according to ICD-10, is a rare autoimmune disease associated with presynaptic impairment of neuromuscular transmission due to the production of antibodies to voltage-gated calcium channels. The disease is characterized by variable muscle weakness of the proximal limbs, mainly the gluteal and femoral muscles, ptosis of the eyelids, diplopia, dysarthria and peripheral paresthesia, and decreased tendon reflexes. The peculiarity of the Lambert-Eaton myasthenic syndrome is manifested in a combination of increased muscle weakness and fatigue with the phenomenon of "working in" - an increase in muscle strength against the background of muscle load after a short-term maximum contraction. At the same time, the patient shows normal response of tendon reflexes. Myasthenic Lambert-Eaton syndrome is often associated with small cell lung cancer and very rarely develops with tumors of other localization. We observed an 80-year-old patient with complaints of weakness and pain in the hips, shoulders, pelvic region, half-ptosis of the eyelids. For half-ptosis of the eyelids, a differential diagnosis was made 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 later was undergoing surgical treatment. This case illustrates Lambert-Eaton's paraneoplastic myasthenic syndrome, a rare tumor form associated with thyroid cancer. Key words: LambertEaton myasthenic syndrome, paraneoplastic syndrome, thyroid cancer.