A Rare Case of Autoimmune Enteropathy Associated With Lambert-Eaton Myasthenic Syndrome and a Literature Review.

Autoimmune enteropathy is a rare intestinal disease characterized by chronic diarrhea and severe malabsorption in the presence of circulating autoantibodies against enterocytes and goblet cells, typically affecting children or young adults. Lambert-Eaton myasthenic syndrome (LEMS) is also a rare autoimmune neuromuscular junction disorder characterized by muscle weakness due to antibodies against the P/Q-type voltage-gated calcium channels (VGCCs) on the presynaptic nerve terminals. We report a case of concurrent diagnoses of autoimmune enteropathy and LEMS in a 24-year-old female patient with a history of autoimmune thyroiditis and vitiligo. The diagnosis of LEMS was established by the typical electromyographic findings and positive antibodies against P/Q-type VGCCs. After malignancies were excluded, treatment with rituximab in combination with intravenous immunoglobulin led to improvement. Within two months of the LEMS diagnosis, the patient presented with severe muscle weakness, chronic diarrhea, vomiting, and weight loss. After a thorough work-up, the diagnosis of autoimmune enteropathy was made, based on severe villous atrophy with a dense inflammatory infiltrate in duodenal biopsies and the exclusion of other causes of chronic diarrhea and non-celiac enteropathy. The patient was treated successfully with total parenteral nutrition, corticosteroids, and azathioprine. To our knowledge, this is one of the first reports of autoimmune enteropathy associated with LEMS.