Pseudomelanosis duodeni and the controversial pigment--a clinical study of 4 cases.

Despite the common practice of upper gastrointestinal endoscopy, the unique phenomenon of punctate black pigmentation of the duodenal mucosa, now known as pseudomelanosis duodeni, still remains a rare entity. Four patients with normal renal function at presentation were found to have this pigment on endoscopy. One developed renal failure subsequently but the pigmentation persisted and this observation has not been reported before. Histochemical and ultrastructural studies were made. It is postulated that the pigment is heterogenous and represents a form of stored iron. Anti-hypertensive drugs may have a role in the causation of the pigmentation formation.