methemoglobinémiát

Methemoglobinémia is a blood disorder characterized by an abnormally high level of methemoglobin. Methemoglobin is a form of hemoglobin that is unable to bind and transport oxygen from the lungs to the rest of the body. Hemoglobin is the protein in red blood cells responsible for carrying oxygen. In methemoglobinémia, the iron in hemoglobin is in the ferric (Fe3+) state instead of the more common ferrous (Fe2+) state. This change in iron oxidation prevents oxygen from binding effectively.

This condition can be congenital, meaning it is inherited, or acquired. Congenital methemoglobinémia is typically caused by genetic defects in the enzymes that reduce methemoglobin back to its functional form. The most common inherited form is methemoglobinémia type I, caused by a deficiency in cytochrome b5 reductase. Acquired methemoglobinémia can result from exposure to certain drugs, chemicals, or toxins. Examples include nitrates, nitrites, certain anesthetics like prilocaine, and some antibiotics like sulfonamides. Ingestion of contaminated well water containing nitrates can also lead to this condition, particularly in infants.

Symptoms of methemoglobinémia vary depending on the level of methemoglobin in the blood. Mild cases may be asymptomatic or cause slight cyanosis, a bluish discoloration of the skin and mucous membranes. As levels increase, symptoms can include headache, dizziness, fatigue, shortness of breath, and rapid heart rate. Severe methemoglobinémia can lead to seizures, coma, and even death. Diagnosis is confirmed by blood tests measuring methemoglobin levels. Treatment depends on the cause and severity, with methylene blue being a common antidote for acquired cases. Genetic counseling and supportive care are important for congenital forms.