The patient in our case study is a 6-month-old female whose father brings her to be evaluated by her physician. The patient presents with faintly blue skin and mucous membranes. Her breathing is normal and she does not present with any other symptoms. Her blood is drawn and is found to have a slight brown cast. In completing a differential diagnosis, it is important to review the normal physiology of the respiratory system. The respiratory system has four functions including exchange of gases between the atmosphere and the blood, homeostatic regulation of body pH, protection from inhaled pathogens and irritating substances, and vocalization. The respiratory system carries out these functions by exchanging air between the environment and the …show more content…
Under oxidative stress, iron is converted into the ferric state (Fe3+). When iron is converted from its ferrous form to is ferric state, hemoglobin is converted to methemoglobin. Methemoglobin lacks the electron that is necessary to form a bond with oxygen. As a result, methemoglobin is not capable of oxygen transport (Wikipedia). The hexose-monophosphate shunt pathway and the enzyme systems of diaphorase I and diaphorase II are mechanisms that regulate levels of methemoglobin in the human body. Diaphorase I is the major regulatory system involved in keeping methemoglobin levels low, removing 95-99% of the methemoglobin that is produced in the body under normal circumstances. Diaphorase I relies of cytochrome b5 reductase to transfer electrons from NADH to methemoglobin while diaphorase II relies on G6PD to reduce methemoglobin to hemoglobin (Medscape). Disruption to methemoglobin regulation can be a serious medical issue. In some deficiencies, cytochrome B6 is absent in red blood cells or in all cells of the body. In other deficiencies, abnormal hemoglobin is present which allows for the oxidation of iron into the ferric state. Both of these deficiencies cause a decreased ability for oxygen to be released to tissues and can result in hypoxia due to a decreased …show more content…
Symptoms of type 1 methemoglobinemia include a bluish coloring of the skin and/or mucous membranes while symptoms of type 2 methemoglobinemia may include developmental delay, intellectual disabilities or seizures. Symptoms of acquired methemoglobinemia may include a bluish coloring to the skin, headache, fatigue, shortness of breath and lack of energy (Medline Plus). Symptoms are proportional to the fraction of methemoglobin in the blood and may be better explained by methemoglobin percentages. A normal methemoglobin fraction is about 1% and individuals with 3-15% methemoglobin levels may experience a slight blue or grey discoloration of their skin. Individuals with 15-25% methemoglobin levels may be relatively asymptomatic apart from mild cyanosis while individuals with 25-50% methemoglobin levels may experience symptoms including headache, dyspnea, lightheadedness, weakness, confusion, palpitations, and chest pain. Methemoglobin levels of 50-70% are dangerous and may involve cardiac arrhythmias, altered mental status, delirium, seizures, coma, and acidosis. Methemoglobin levels greater than 70% typically result in death