The thymus in hemochromatosis.

Although iron in cases of hemochromatosis has been described in virtually every organ, its presence in the thymus has only been rarely observed. While investigating all cases of hemochromatosis autopsied at The Johns Hopkins Hospital over the past decade, 4 adult cases in which the thymus was available for histologic study were examined in light of recent documentation of this organ's role in lymphopoiesis and secretory activity. Iron-containing moieties were found within both lymphocytes and epithelial cells of these involuted thymic glands. The thymic iron suggests either an uptake of iron moieties from the vascular pool or their synthesis within the cell itself. While the former mechanism provides evidence against the existence of an impermeable blood-thymus barrier, the latter supports the existence of a metabolically active gland with complex function.