Pseudomelanosis duodeni is a rare condition in which dark pigment accumulates in macrophages located in the lamina propria of the duodenal mucosa. Three cases are reported here and the literature is reviewed. No clinical association can be found that points clearly to the underlying etiology. Electron probe x-ray microanalysis was used to study the pigment in macrophage granules in 2 of our patients and demonstrated high iron and sulfur content. Iron accumulation in ferritinlike particles was detected in absorptive cell lysosomes. A possible mechanism for the accumulation of absorbed iron by macrophages is considered.
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