Methemoglobinemia

Mehemoglobinemia is a blood disorder that is characterised by more methemoglobin in the blood than normal. This condition impairs the blood's ability to carry oxygen in the blood. It can either be acquired or inherited.   

1. Acquired is the most common (uncommon), and results from the person's exposure to oxidizing substances that overwhelm the body's natural enzyme systems. Examples of these substances are listed below. 

• Medications: local anesthetics  (benzocaine, lidocaine antibiotics (like dapsone and chloroquine, and nitrates. 
• Chemicals/foods: nitres (used as food preservatives, fertilizers used in farming, or found in certain foods.

2. Inherited is caused by congenital defects (rare). The two main forms are:

• enzyme deficiency: cytochrome is the most common problem.

             Type 1: only affects the red blood cells; often presents with mild or no symptoms.                  Type 2: affects all cells and is much more severe, often causing developmental delays, neurological impairment, and premature death.

• Hemoglobin M Disease: a defect in the hemoglobin protein structure itself that makes the iron more easily oxidized.

Symptoms vary based on the level of methemoglobin in the blood, the underlying cause, and the patient's overall health.    An important clue is that the arterial blood appears to be chocolate brown rather than the normal bright red.   Treatment focuses on restoring normal hemoglobin function and is often an emergency in severe cases. 

• Methylene Blue: is the best treatment for this acquired condition. 
• Supportive Care: supplemental oxygen helps, but is not a cure.
• Discontinuation of Offending Agent: to stop consuming the agent.
• Alternative Treatments: ascorbic acid (vitamin C), byperbaric oxygen therapy, or blood transfusion.