HBG2 and methemoglobinemia: Acquired methemoglobinemia can result from exposure to certain pharmaceutical preparations (e.g. lidocaine, benzocaine, sulfonamides, dapsone, nitroglycerine) or chemical substances (e.g. nitrates, copper, sulfate, chlorite, chloramines and chlorates), which may cause oxidation of hemoglobin to methemoglobin faster than methemoglobin is reduced back to hemoglobin [14].