Final answer:
Methemoglobinemia, according to E.M. Scott, is speculated to be caused by a lack of glutathione, a compound preventing the oxidation of hemoglobin in red blood cells.
Step-by-step explanation:
According to E.M. Scott, the speculation is that methemoglobinemia is caused by a lack of glutathione. Methemoglobinemia occurs when the iron in hemoglobin is oxidized from its normal ferrous (Fe²⁺) state to ferric (Fe³⁺), rendering it incapable of binding oxygen, which disrupts its ability to transport oxygen to the body's tissues. Glutathione acts as a peroxidase, preventing the oxidation of hemoglobin and the consequent increase in the percentage of methemoglobin.
Higher levels of methemoglobin can lead to symptoms such as cyanosis and dyspnoea. It is noteworthy that methemoglobin can be helpful in treating cyanide poisoning by forming cyanomethemoglobin, which prevents the toxic effects of cyanide.
Diseases that affect hemoglobin's structure or function, such as sickle cell anemia and thalassemia, significantly compromise the blood's oxygen-carrying capacity. These conditions, along with external factors like certain drugs and exposure to industrial chemicals, can elevate methemoglobin levels, leading to methemoglobinemia.