2638 Intestinal Pseudo-Obstruction Associated With Seropositive Myasthenia Gravis, Thymoma, and Positive CV-2 Antibodies

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INTRODUCTION: Intestinal pseudo-obstruction (IPO) is a rare condition characterized by signs and symptoms of bowel obstruction without an identifiable mechanical cause. Antibody-mediated paraneoplastic syndromes and autoimmune diseases have been reported as two potential etiologies. We report a unique case of IPO presenting with thymoma, myasthenia gravis (MG), and positive CV-2 antibodies. CASE DESCRIPTION/METHODS: A 43 year old previously healthy female presented to the ED with abdominal pain, nausea and vomiting. This was her third visit to the ED in the past week for similar symptoms. On admission, laboratory studies were normal. A CT of the abdomen revealed marked gastric and small bowel distention, fecal impaction, and a mediastinal soft tissue density (Figure 1). She was initially managed medically with restriction of oral intake, intravenous fluids, and a nasogastric tube. Since she did not improve after several days, she was taken to the operating room for a diagnostic laparoscopy, which did not show evidence of mechanical obstruction. A CT chest with contrast done to investigate the mediastinal soft tissue density revealed an anterior mediastinal mass.A chest MRI had changes suggestive of a thymoma. This was subsequently confirmed by biopsy. Given the suspicion for a paraneoplastic process, multiple serologic markers were ordered. Acetylcholine receptor (AChR) antibodies and CV-2 antibodies were positive (Table 1). She was diagnosed with paraneoplastic intestinal pseudo-obstruction. The patient was treated with IV methylprednisolone and pyridostigmine with marked improvement in symptoms. DISCUSSION: The association of IPO as a paraneoplastic syndrome of thymoma and myasthenia gravis has been reported in only a few cases. The pathophysiology involves AChR antibodies targeting the neuronal nicotinic acetylcholine receptors present on autonomic ganglia. Our patient had positive AChR antibodies. She had no other symptoms of MG, indicating isolated autonomic dysfunction. IPO has also been associated with malignancies such as small cell lung cancer, which may be mediated by a variety of autoantibodies. Anti-Hu antibody has been most commonly implicated but was negative in this case. Anti-CV2 antibody was positive, which was reported in only one previously published case. In summary, patients with thymomas or MG should have testing for paraneoplastic antibodies; they tend to respond to treatment with immunosuppression and acetylcholinesterase inhibitors.