I saw this biopsy yesterday and thought it was a curious little finding--pseudomelanosis duodeni is the lovely and impressive name given to this rare but apparently harmless and incidental entity.
The patient is a 73-year-old woman with a history of recent GI bleeding, chronic anemia, diabetes mellitus, hypertension, CAD/CHF, and chronic renal disease, and CML with hemoccult-positive stool and hemoglobin 6.2 gm/dL and symptomatic anemia requiring RBC transfusions. She underwent upper and lower GI endoscopy. Her endoscopic examination of the duodenum was described as unremarkable and biopsies were obtained to exclude villous atrophy. The stomach was described as showing mild diffuse antral gastritis without erosions or ulcers. Antral biopsies showed features consistent with mild reactive gastropathy and were negative for Helicobacter. The colonoscopy was remarkable for a transverse colon polyp which histologically was a traditional serrated adenoma.
Pseudomelanosis duodeni is a benign, rare, incidental finding that has been described in various case reports a being asymptomatic and associated with a variety of systemic diseases and medications. Chronic renal disease, hypertension, oral iron supplementation, and gastric hemorrhage have been most frequently described in association with this entity. Unlike melanosis coli, it is not associated with anthraquinone laxative use. The histopathologic changes described correspond with the photomicrographs above, viz., accumulation of dark-brown/black pigmented macrophages in the subepithelial lamina propria often at the tips of villi. The endoscopic appearance has been described as discrete, small, flat brown-black spots in the duodenal mucosa imparting a speckled appearance. The histological differential diagnosis of pigmented, iron-positive cells in the small bowel includes hemosiderosis/hemochromatosis (which was a clinical possibility in this case) but the distribution of pigment is in epithelial cells and Brunner's gland as opposed to macrophages in pseudomelanosis duodeni. The cause and natural history are unknown.