What is Methemoglobinemia?

Methemoglobinemia or Met h-b is a rare blood disorder that may be caused by an inherited or congenital condition, exposure to toxins, especially nitrates, or dehydration, particularly in infants. In this condition, methemoglobin, a form of hemoglobin is present in too great a quantity. This particular type of hemoglobin cannot carry or bind oxygen, which means that the number of red blood cells containing oxygen is reduced. Poor supply of oxygen bearing red blood cells causes anemia, and can be disastrous to the organs, and when methemoglobin is present in large amounts, organs can begin to fail. Thus the condition can be fatal, causing total cardiac failure when it remains untreated.

Usually, methemoglobinemia is noticed prior to organ failure, especially in light-skinned people. It will cause cyanosis, distinctly blue skin. People who have this disorder look not just a little blue, but frequently very blue. Other symptoms include changes in mental status, confusion, shortness of breath, dizziness, and headaches. Continued build-up of methemoglobin can cause loss of consciousness, coma and eventually death. Diagnosis can be confirmed by checking the presences of methemoglobin in the blood, which should be less than 1%. Higher amounts confirm methemoglobinemia. Further, blood from arteries looks brown instead of bright red.

The condition is treatable, and may need to be retreated in people who have congenital or inherited methemoglobinemia by attempting to reduce methemoglobin so that the iron molecules will again carry oxygen. This is normally accomplished through intravenous drips of the substance methylene blue. As treatment progresses, skin begins to pink up and the body’s major organs are better oxygenated.

While methemoglobinemia may be inherited, incidence of inheritance is low. Instead, the disease normally manifests after severe dehydration or exposure to toxins. In a 2007 episode of the spin-off show of Grey’s Anatomy, Private Practice, several sisters developed the condition after long exposure to nitrate fertilizers. This is actually a perfect example of how certain toxins can create the condition.

Infants, especially those less than six months old, are also very vulnerable to methemoglobinemia if they get illnesses that result in dehydration. Young children are especially prone to dehydration from diarrhea or vomiting because their body weight is so low. Unlike adults, they can become dehydrated within a few hours of getting ill, which can create excess levels of methemoglobin quickly. This is why it is extremely important to treat young children with severe diarrhea or vomiting immediately, especially if the condition doesn’t resolve within a few hours, and the child cannot tolerate or keep down any fluids.