Causes
MetHb condition can be:
- Passed down through families (inherited or congenital)
- Caused by exposure to certain medicines, chemicals, or foods (acquired)
- There are two forms of inherited MetHb. The first form is passed on by both parents. The parents usually do not have the condition themselves. They carry the gene that causes the condition. It occurs when there is a problem with an enzyme called cytochrome b5 reductase.
There are two types of inherited MetHb:
- Type 1 (also called erythrocyte reductase deficiency) occurs when RBCs lack the enzyme.
- Type 2 (also called generalized reductase deficiency) occurs when the enzyme doesn't work in the body.
The second form of inherited MetHb is called hemoglobin M disease. It is caused by defects in the hemoglobin protein itself. Only one parent needs to pass on the abnormal gene for the child to inherit the disease.
Acquired MetHb is more common than the inherited forms. It occurs in some people after they are exposed to certain chemicals and medicines, including:
- Anesthetics such as benzocaine
- Nitrobenzene
- Certain antibiotics (including dapsone and chloroquine)
- Nitrites (used as additives to prevent meat from spoiling)
| type | factor |
|---|
| type 1 | inherited |
| haemoglobin M desease | genetic mutation |
| type 2 | reductase deficiency |