Methemoglobin: An Unlikely Explanation for Cyanosis Methemoglobinemia is an uncommon but possible

2500 WordsApr 23, 201910 Pages
Methemoglobin: An Unlikely Explanation for Cyanosis Methemoglobinemia is an uncommon but possible reason for cyanosis. Methemoglobinemia is significant because the disease is fairly rare and consequently most physicians do not consider it as a cause when diagnosing a patient with cyanosis. Regrettably, patients often get misdiagnosed and sometimes treated for the wrong disorder as a result. A two fold dilemma occurs when the patient is treated for an incorrect disorder. The first part of the dilemma includes the patient experiencing all of the negative side effects of the wrong treatment, and gaining no benefit. The second part of the dilemma is that the patient’s actual medical condition is not being treated, and is getting worse…show more content…
This family has a hemoglobin disorder known as congenital methemoglobinemia [6]. Methemoglobinemia is a hemoglobinopathy where the concentration of methemoglobin in the blood is more than 1% of the total hemoglobin [3]. Normal hemoglobin has a reduced ferrous iron (Fe 2+) while methemoglobin has an oxidized ferric iron (Fe 3+). The change in valence prevents methemoglobin from being able to carry oxygen [4, 9]. There are mechanisms in place to reduce the amount of methemoglobin in the blood [2]. Cytochrome b5-Methemoglobin reductase and nicotinamide adenine dinucleotide phosphate (NADPH) methemoglobin reductase enzymes are responsible for reducing the amount of methemoglobin in the blood [9]. Methemoglobinemia can be either acquired or congenital. When methemoglobinemia is acquired the mechanism that reduces methemoglobin is not able to keep up with the amount of oxidation that is occurring due to the various methods of acquiring methemoglobinemia [2]. There are two primary reasons for congenital methemoglobinemia; either there is a presence of an abnormal structure of the hemoglobin molecule, called hemoglobin M, or a deficiency in the enzymes cytochrome b5 methemoglobin reductase or glucose-6-phosphate dehydrogenase (G6PD) [5]. There are two main types of congenital methemoglobinemia, type I and type II. Type I methemoglobinemia is where the enzyme deficiency only affects the erythrocytes, and is easily

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