S6091 Pigment on the Path: A Case Series of Duodenal Pseudomelanosis From a Single Institution

Introduction: Duodenal pseudomelanosis is an extremely rare, benign condition typified by the presence of dark pigmented spots in the duodenal mucosa. First described in 1976, pseudomelanosis duodeni continues to be an incidental finding on endoscopy and has an unclear clinical significance. Herein, we describe a case series of duodenal pseudomelanosis diagnosed at our institution. It is important for clinicians to recognize duodenal pseudomelanosis, given its tendency to mimic serious conditions, such as melanoma, metastatic disease, and drug-induced pigmentation. Case Description/Methods: Case 1: A 74-year-old man with a history of end-stage renal disease (ESRD) on HD, type 2 diabetes, and hypertension was brought to the emergency department for acute-onset epigastric pain and melena. Triage labs: hemoglobin, 5.3 g/dL, and BUN, 90 mg/dL. Esophagogastroduodenoscopy (EGD) revealed a small hiatal hernia, 3 gastric nodules with no stigmata of recent bleeding, and distal antral and duodenal melanosis. Duodenal bulb specimens showed black granular pigment within the macrophages of the lamina propria, which stained positive for iron, consistent with pseudomelanosis. Case 2: An 86-year-old man with a history of ESRD on HD, hypertension, and obscure GI bleeding was brought to the emergency department for altered mental status and fever. Triage blood tests: low hemoglobin (4.7 g/dL) and leukocytosis (WBC, 14.4 × 103/mm3). Prior endoscopic procedures were non-revealing. EGD showed erythematous duodenopathy and severe melanosis in the second portion of the duodenum. No biopsies were obtained for histopathological analysis and the patient was managed conservatively. Case 3: A 79-year-old woman with a history of acute ischemic stroke, hypertension, type 2 diabetes, and iron deficiency anemia requiring iron sucrose infusions presented to the emergency department complaining of acute-onset abdominal pain. Labs: low hemoglobin, 7.8 g/dL. Imaging revealed prominent colitis and proctitis without perforation or abscess formation. EGD showed a small hiatal hernia, atrophic bile gastritis, and diffuse duodenal melanosis. Histopathology findings were consistent with duodenal pseudomelanosis. Discussion: The etiopathogenesis of duodenal pseudomelanosis is not fully understood, but it has been associated with some chronic illnesses and certain medications. The diagnosis of pseudomelanosis is made based on endoscopic findings of dark-speckled mucosal pigmentation and often confirmed on histology. Recognizing this novel entity is crucial for accurate diagnosis, appropriate management of associated conditions, and avoiding unnecessary interventions.