Second spectroscopically abnormal methemoglobin associated with hereditary cyanosis.

Isolation of an abnormal methemoglobin from two families exhibiting dominantly transmitted cyanosis have permitted the recognition of two different pigments of the hemoglobin M type. It is possible that the abnormal properties which characterize the acidic methemoglobin derivatives result from a crevice configuration of the heme, with two Feprotein bonds.