Methemoglobinemia is a condition that can be passed down through generations or it can be drug induced. In cases where methemoglobinemia is passed down, genes are altered which results in a deficiency of a NADH-dependent enzyme which aids in the reduction of methemoglobin. Without the presence of this enzyme, cytochromes cannot be reduced, and therefore methemoglobin cannot be reduced back to hemoglobin. In cases of methemoglobinemia, patients have too much methemoglobin in their system, decreasing the availability of oxygen throughout the body. When methemoglobinemia is drug-induced it is often reversible, but when it is passed down in families it is not. Patients will usually present with cyanosis (blue coloring of the skin) as one of the main symptoms and it can be managed.
There are a few different types of methemoglobinemia. One of which is autosomal recessive congenital methemoglobinemia (RCM) type II and new treatments are being explored since this type could result in intellectual disability, dysphagia, movement disorders, progressive decline of quality of life, and life expectancy is reduced. One treatment option that is being explored is methylene blue, which has been shown in a few studies to reduce methemoglobin with no rebound methemoglobinemia after 24 hours of dosage.
Data on methylene blue treatments is very scarce, and I think studying this treatment further would be very valuable. Since there is no current way for a full cure of methemoglobinemia that is passed down, treatments like methylene blue are the best bet for people who may be experiencing intellectual disability, dysphagia, and movement disorders. If used in babies born with the condition, I think use of methylene blue as soon as possible may help lessen the effects of having the condition. Until genes can be safely edited in humans using CRISPR-Cas9, I think methylene blue treatments will be the best and safest option for patients in the meantime.
Congenital Methemoglobinemia Type II - Clinical Improvement with Short-Term Methylene Blue Treatment: