What is Methemoglobinemia?

The ferrous iron in the co-heme of the hemoglobin molecule is oxidized to trivalent iron, which becomes methemoglobin (MHb), and loses oxygen function. Normal red blood cells can use NADH to reduce MHb to Hb under the catalysis of cytochrome b5 reductase. Once MHb is elevated in the blood, it is called MHbemia. Toxic MHbemia is more common, with a history of exposure to certain drugs or poisons (such as nitrite, phenacetin, procaine, aniline, etc.), and infant diarrhea is also a common cause. Congenital MHbemia is rare and is mainly caused by a deficiency of cytochrome b5 reductase.

Methemoglobinemia

The ferrous iron in the co-heme of the hemoglobin molecule is oxidized to trivalent iron, which becomes methemoglobin (MHb), and loses oxygen function. Normal red blood cells can use NADH to reduce MHb to Hb under the catalysis of cytochrome b5 reductase. Once MHb is elevated in the blood, it is called MHbemia. Toxic MHbemia is more common, with a history of exposure to certain drugs or poisons (such as nitrite, phenacetin, procaine, aniline, etc.), and infant diarrhea is also a common cause. Congenital MHbemia is rare and is mainly caused by a deficiency of cytochrome b5 reductase.

1. The skin, lips, mucous membranes, and nail beds show obvious cyanosis.

2. Toxic MHbemia, which can be acute or slow. Sudden onset symptoms are obvious, accompanied by headache and fatigue. In severe cases, the MHb content can account for 50-70% of the total Hb, which can appear

Diagnose based on

1. The skin, lips, mucous membranes, and nail beds show obvious cyanosis.

2. Toxic MHbemia can occur suddenly or collectively, with a history of drug or poison exposure. Congenital persons develop symptoms since childhood and have persistent cyanosis for many years.

3. Take a drop of peripheral blood on the filter paper, the blood is chocolate-like brown-red, and it will not change to bright red in the air for 1 minute. This test can rule out hypoxic cyanosis caused by respiratory or reflux failure.

Principles of methemoglobinemia treatment

1. Congenital MHbemia does not require treatment. Riboflavin and large amounts of vitamin C can reduce MHb content.

2. Toxic MHbemia with obvious symptoms, and those with MHb content exceeding 20% should be treated in time.

Methemoglobinemia medication principles

1. Hereditary glucose-6-phosphate dehydrogenase (G6PD) deficiency is common in Guangdong, Guangxi, Yunnan, Sichuan and other provincial populations. NADPH cannot be provided due to G6PD deficiency.

2. If the MHb content is less than 10%, it can be closely observed and usually heals on its own.