A COMPARISON OF THE ULTRASTRUCTURE OF PIGMENT GRANULES IN MELANOSIS-ILEI AND PULMONARY LYMPH-NODES

Two cases of melanosis ilei were studied, in which grossly visible bla ckish pigmentation of the ileal mucosa was incidentally discovered at autopsy. Light microscopy showed that the pigment granules lay within macrophages in atrophic Peyer's patches. Ultrastructural studies showe d that the pigment granules were heterolysosomes containing crystallin e material, particles, granules and, occasionally, lipid droplets. The morphological similarity between these pigment granules and granules in pulmonary macrophages was established through ultrastructural studi es of pulmonary lymph nodes obtained during routine autopsies. These d ata, plus results of past electron-probe X-ray analytic studies by us and others, leads us to conclude that the pigment granules in melanosi s ilei contain exogenous material derived from inspired and ingested m aterials.