Abstract
RATIONALE Approximately 0.001% of patients with cancer have paraneoplastic nerve system syndrome, which can affect the central nervous system, neuromuscular junction, or peripheral nervous system. Although myasthenia gravis (MG) may exist as a thymic paraneoplastic syndrome (PNPS), its association with primary lung cancer remains unknown. PATIENT CONCERNS A 55-year-old female presented with slurred speech, weakness in chewing, sporadic difficulty in swallowing, and weakness in both lower limbs for half a year. DIAGNOSES Based on cerebrospinal fluid and electromyography findings, we present the case of a female patient diagnosed with overlapping multicranial nerve tumor infiltration and MG-like neurological PNPS secondary to lung adenocarcinoma. INTERVENTIONS The patient received intrathecal injections of pemetrexed and neurotrophic (vitamin B) therapy before ceasing chemoradiotherapy and chose cabozantinib on her own. OUTCOMES Weakness of the proximal limbs, choking cough, and chewing problems did not improve significantly. LESSONS Although it is unclear why MG coexists with lung cancer, it is probable that MG is a paraneoplastic condition. Cerebrospinal fluid testing should be carried out along with electrophysiological, serological, and pharmacological procedures pertinent to the diagnosis of MG to thoroughly examine if people simultaneously experience MG-like PNPS and tumor growth. Starting immunotherapy and anticancer medication at the same time that tumor development and MG-like syndrome are discovered is crucial.
