Mast cell phagocytosis of melanosomes in a case of Rothmund-Thomson's congenital poikiloderma*

Abstract

Summary Individual mastoeytes containing both typical mast cell granules and melanosomes were observed in the upper dermis in a case of Rothmund-Thomson's congenital poikiloderma. The mastocytes were often closely associated with macrophages containing melanosomes. Several melanosome complexes were found within mastocytes; some were included in mast cell granules of particularly large size, while others were confined in phagoevtic vacuoles, or seemed to lie free within the cytoplasm. All of the melanosomes were Stage IV, with no evidence of formative stages, suggesting that they had come from outside the cell.