ABSTRACT
Ferrihemoglobin is of chocolate color; the presence of this dark pigment, 1.5 g or more per 100 ml of blood, causes cyanosis. In humans quick transformation of about 30% of the hemoglobin into ferrihemoglobin increases the heart rate on standing by 10 beats per min, but otherwise causes little discomfort. Few data are available on the maximal ferrihemoglobin content of blood survived by humans. Survival with ferrihemoglobinemia also depends on quality and intensity of additional actions of the ferrihemoglobin-forming substance. The role ferrihemoglobinemia plays in the toxicity of a substance varies widely with species. Normal pregnancies have been observed with hereditary ferrihemoglobinemia and humans 60 to 80 years of age with hereditary ferrihemoglobinemia have been recorded. Since many substances which in vivo produce ferrihemoglobin also cause formation of Heinz bodies in red cells, some authors supposed that ferrihemoglobin is an essential intermediate in the mechanism of Heinz body formation.
