LAUSR

A 27-year-old East Asian woman with history of metastatic thymoma was evaluated for a 2-year history of non-bloody chronic watery diarrhea. As an outpatient, she had been evaluated on multiple occasions due to profuse, watery diarrhea that occurred seven times a day. She underwent colonoscopy after 6 months of symptoms, which was normal except for internal hemorrhoids. Computed tomography (CT) of the abdomen/pelvis demonstrated new diffuse circumferential wall thickening of the terminal ileum, cecum, and ascending colon. Stool studies for infectious agents were negative. Upper endoscopy and colonoscopy a month prior to presentation demonstrated possible colitis. Colon biopsies demonstrated crypt abscesses and cryptitis as well as neutrophilic infiltrates in the lamina propria. She was trialed on budesonide 9 mg daily without improvement. The patient’s metastatic thymoma history extended to 2014, when she noted intermittent left-sided chest wall pain. CT of her chest demonstrated an anterior mediastinal mass measuring 6.1 × 6.8 × 6.4 cm and at least three pleuralbased masses. Biopsies were consistent with thymoma. The patient received neoadjuvant chemotherapy with cisplatin, doxorubicin, and cyclophosphamide, followed by thymectomy with resection of the anterior mediastinal mass with en bloc pericardium, lung, and left phrenic nerve. She received radiation following the surgery and later developed immune thrombocytopenia that required a course of rituximab. She had a follow-up chest CT that demonstrated progressive pleural thickening in the left medial posterior hemithorax. The patient refused further chemotherapy. During her hospitalization at Stanford Hospital, the patient had normal electrolytes and thyroid hormone levels, as well as negative stool studies for infectious causes. Her immunoglobulins were normal to slightly elevated. C3 and C4 levels were within normal range. Magnetic resonance enterography (MRE) demonstrated normal-appearing small bowel, terminal ileum, and colon. Owing to a body mass index of 12, she was started on total parenteral nutrition (TPN). Upper endoscopy revealed white esophageal plaques with normal stomach and duodenum (Fig. 1). Colonoscopy demonstrated congested mucosa in the rectum and throughout rest of the colon, as well as in the terminal ileum (Fig. 2). Biopsies throughout the duodenum, terminal ileum, and colon demonstrated near-complete absence of goblet cells, endocrine cells, and Paneth cells, with accompanying acute and chronic inflammation. Microscopic examination of the small bowel revealed villous blunting, whereas the colon showed active cryptitis with scattered crypt apoptotic bodies present (Fig. 3a, b), with no granulomas seen. Given the clinical context, these histomorphologic findings elevated the suspicion for autoimmune enteropathy. Anti-enterocyte antibodies had a strongly positive IgG signal for goblet cell cytoplasm and luminal mucin. The patient was started on intravenous steroids, which improved her diarrhea. She was seen as an outpatient by gastroenterology and by thoracic oncology 2 months after discharge and continues to do well on a tapering regimen of oral steroids and has since gained 26 lb. Her bowel movements are now occurring two–three times a day, significantly improved from before. * Mike Tzuhen Wei [email protected]