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A Case of Pseudomelanosis Duodeni: Striking Endoscopic Features With Subtle but Characteristic Pathologic Findings


 A 72-year-old man was referred to the inflammatory bowel disease clinic for evaluation for possible Crohn disease. The patient was diagnosed with pan-ulcerative colitis in the late 1960s. He had medically refractory disease and required a total proctocolectomy with end ileostomy in the early 1970s. Since surgery, the patient has done well with his end ileostomy and has not required any inflammatory bowel disease medications. Over the past 14 months, he has developed intermittent foul-smelling serosanguinous drainage from his previous drained pilonidal cyst. His local gastroenterologist raised the concern for possible Crohn disease with perianal involvement. He has a significant family history of Crohn disease in his father. Past medical history includes chronic kidney disease, hypertension, diabetes, coronary artery disease, gout, and arthritis. Esophagogastroduodenoscopy (EGD) revealed diffuse brown to black speckled/tigroid spots in the entire examined duodenum. Duodenal biopsy showed scattered clusters of macrophages containing dark pigmented granules within the apical tips of the lamina propria. These pigmented granules were focally positive with iron staining. No villous blunting, intraepithelial lymphocytosis, granuloma, or significant inflammation was identified. The distinctive endoscopic and histologic features are diagnostic of pseudomelanosis duodeni. Pseudomelanosis duodeni is a rare benign entity characterized by diffuse black tigroid spots and aggregates of pigment-laden macrophages in the lamina propria. Results of iron staining are characteristically variable. Pseudomelanosis duodeni is seen in middle-aged to elderly adults. Most of the patients with pseudomelanosis duodeni are asymptomatic. Although the exact etiology remains unknown, pseudomelanosis duodeni has been reported to be associated with several medical conditions such as end-stage renal disease, hypertension, diabetes, heart failure, gastrointestinal hemorrhage, and medications, including oral iron therapy, furosemide, hydralazine, thiazide, and iron sulfate. Pathologists should be aware of this rare condition of the duodenum to make an accurate diagnosis of this rare entity.