"Melanosis" of the duodenum associated with a gastric ulcer and folic acid deficiency.

Melanosis involving the duodenum is extremely rare. We present endoscopic, microscopic, and histochemical studies of a patient with melanosis of the duodenum associated with a gastric ulcer and a folic acid deficiency. The pigment is similar to that observed in melanosis coli and histochemically does not stain like melanin or lipofuscin. The pigment disappeared with correction of the folate deficiency and healing of the gastric ulcer, suggesting a possible relationship with these entities.