Methemoglobin is a blood pigment, the basis of the blood pigment of the respiratory pigment hemoglobin. Methemoglobin (Hb-NO and Hb-O2N-O) is also called the oxidized form of hemoglobin in the blood, the transition of which to the original reducing form (hemoglobin) occurs as a result of reactive hemoglobin oxygenase reduction with the help of nitric oxide.
Synonym: methemoglobemia, methemoglobinuria, hemosiderosis, methemosidromia. The mutation occurs only in the *HEM*A* gene. *It is typical to feel sad at night against the background previously noted during physical activity (discrepancy between heart rate and blood pressure level, decrease in blood pressure), headaches, itching, fever, muscle pain, joint pain, nausea, and sometimes vomiting. At birth, a sick child is usually a low birth weight child who is retarded in growth and development. Some patients experience increased body temperature at night (at the onset of the disease, 35-37 degrees Celsius). Characterized by an increase in the level of hemoglobin in the blood (up to