Ultrastructure and electron-probe x-ray analysis of the pigment in melanosis duodeni.

A patient with peptic ulceration developed melanosis duodeni, which was studied by light microscopy, histochemistry, electron microscopy and electron-probe x-ray analysis. Our studies show that the pigment in melanosis duodeni resides in the lysosomes of macrophages in the lamina propria. The pigment is not melanin or a melanin-like compound as has been claimed by previous workers. On the basis of electron-probe x-ray analytical findings we have concluded that the pigment is essentially FeS. On the basis of the history of this patient and cases reported in the literature we think that the Fe in this pigment is derived from haemorrhage in the gastrointestinal tract. We also found small amounts of Ca, K, Al, Mg, Si, and Ag. It would appear that Al, Mg and Si were probably derived from the biological milieu and/or other drugs and/or food and/or specimen contamination.