Methemoglobinemia
Methemoglobinemia, or methaemoglobinaemia, is a condition of elevated methemoglobin in the blood. Symptoms may include headache, dizziness, shortness of breath, nausea, poor muscle coordination, and blue-colored skin (cyanosis). Complications may include seizures and heart arrhythmias.
| Methemoglobinemia | |
|---|---|
| Other names | Hemoglobin M disease, |
| Chocolate-brown blood due to methemoglobinemia | |
| Specialty | Toxicology, haematology |
| Symptoms | Headache, dizziness, shortness of breath, nausea, poor muscle coordination, blue-colored skin |
| Causes | Benzocaine, nitrites, dapsone, genetics |
| Diagnostic method | Blood gas |
| Differential diagnosis | Argyria, sulfhemoglobinemia, heart failure |
| Treatment | Oxygen therapy, methylene blue |
| Prognosis | Generally good with treatment |
| Frequency | Relatively uncommon |
Methemoglobinemia can be due to certain medications, chemicals, or food or it can be inherited. Substances involved may include benzocaine, nitrites, or dapsone. The underlying mechanism involves some of the iron in hemoglobin being converted from the ferrous [Fe2+] to the ferric [Fe3+] form. The diagnosis is often suspected based on symptoms and a low blood oxygen that does not improve with oxygen therapy. Diagnosis is confirmed by a blood gas.
Treatment is generally with oxygen therapy and methylene blue. Other treatments may include vitamin C, exchange transfusion, and hyperbaric oxygen therapy. Outcomes are generally good with treatment. Methemoglobinemia is relatively uncommon, with most cases being acquired rather than genetic.