Diverse clinical disorders distinct from hereditary
hemochromatosis are associated with accumulation of excess body
iron in heterogeneous patterns and through various mechanisms. A deranged
iron turnover somehow relates to the altered physiological barrier for
iron absorption in several defined chronic
anemias with ineffective erythropoiesis. Unexcretable excess
iron acquired from transfusions provides a therapeutic challenge. Genetic defects of
proteins essential for transport of
iron into and out of cells (
transferrin and
ceruloplasmin) deprive the erythron of the
metal and cause its accumulation in other vital organs. The
hemochromatosis alleles predictably contribute to an
iron burden from other causes, commonly facilitate the expression of
porphyria cutanea tarda, and their clinical expression may be accelerated by
hereditary hemolytic anemias. Even minimal
iron excess in
liver disease may contribute to the hepatocellular injury from factors such as alcohol and viruses. Uniquely localized
siderosis occurs in the lung and kidney where
iron cannot turn over and causes variable tissue damage. The most devastating
iron overload disorder,
neonatal hemochromatosis, is understood least of all.