Pseudomelanosis
Comments: During a routine endoscopy for Barrett's related dysplasia surveillance, this mucosal abnormality was identified.
On endoscopy, these pigmented areas of mucosa in the antrum, pylorus, and duodenum were seen. This is the classic endoscopic finding of pseudomelanosis of the gastrointestinal tract, whose features include a brownish-black pigmentation of the mucosa in a non-inflamed, random, speckled pattern. There is no apparent associated mucosal thickening or other defects.
Pseudomelanosis has been observed to occur anywhere along the length of the gastrointestinal tract. The pigment of pseudomelanosis has not been completely characterized although ferrous sulfide is commonly found on staining. A recent case series demonstrated that the majority of these patients are taking oral iron therapy, and as well as antihypertensive medication. A history of renal insufficiency is also common.
This pattern is similar to the finding of melanosis coli in right colon as seen here. With both clinical syndromes the pigmentation is found in lamina propria macrophages. The pigmentation in melanosis coli, however, is in the form of lipofucschin, which is a degradation product of anthracine metabolites commonly taken in the form of oral cathartics in the management of chronic constipation.
The diagnosis is of pseudomelanosis may be confirmed on biopsy. Low power view of the duodenal lamina propria demonstrates villi with darkly pigmented cells admixed with inflammatory cells and vessels. The pigment appears to be confined to histiocytes within the lamina propria and does not involve the epithelium.
On higher magnification, the pigment is noted to be granular, black, and fairly uniform.
Pseudo-melanosis may be more subtle as was seen as an incidental finding in this second example during a routine colonoscopy. Here a faint brownish pigmentation can be observed in the terminal ileal mucosa in an otherwise unremarkable exam.
It has been proposed that the sulfides present in various diuretics such as hydrochlorothiazide and furosemide can bind to oral iron, resulting in the pigmented deposition seen here. It is noteworthy that this patient's lengthy medication list included both oral iron replacement therapy as well as furosemide. The iron deposition seen in pseudomelanosis does not suggest either an iron overload state or any metabolic abnormality, nor does the iron need to be treated with chelation therapy.
| Contributed by: |
Mohammad Bilal Harvard Medical School David G. Forcione, M.D. Instructor in Medicine Harvard Medical School Massachusetts General Hospital Peter B. Kelsey, M.D. Assistant Professor of Medicine Harvard Medical School Massachusetts General Hospital |
|
Citation: Bilal, M. & Forcione, DG & Kelsey, PB (Oct 21 2009). Pseudomelanosis. The DAVE Project. Retrieved Feb, 8, 2010, from http://daveproject.org/viewfilms.cfm?film_id=882 Times viewed since Feb 2006: 1278 |
|
