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Disease Profile

Hereditary methemoglobinemia

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset






Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Autosomal recessive methemoglobinemia; Congenital methemoglobinemia


Blood Diseases; Congenital and Genetic Diseases


The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs.

Orpha Number: 621

A rare red cell disorder classified principally into two clinical phenotypes: autosomal recessive congenital (or hereditary) methemoglobinemia types I and II (RCM/RHM type 1; RCM/RHM type 2).

Clinical description
In RCM type 1, cyanosis from birth is the only symptom. It is well-tolerated and is associated with mild complaints of headaches, fatigue and shortness of breath upon exertion. RCM type 2 is much more severe; the cyanosis is accompanied by neurological dysfunction (with intellectual deficit, microcephaly, growth retardation, opisthotonus, strabismus and hypertonia), which usually becomes evident during the first four months of life. Two additional forms of RCM have also been reported. RCM type 3 was the term used to define a phenotype with cyanosis but without neurological abnormalities in which Cb5R deficiency was identified in leucocytes and platelets as well as erythrocytes. This distinction has been largely ignored in subsequent reports of other CYB5R3 variants, so the term RCM type 3 is rarely used. RCM type 4 is a very rare disease associated with chronic cyanosis caused by mutations in the CYB5A gene (18q23) encoding cytochrome b5. In addition, there have been two reports of NADPH reductase deficiency, but in one case (identified though an inability to metabolize methylene blue) methemoglobinemia was not present suggesting that this pathway has limited physiological importance. It is also possible that mutations of the substrate of NADPH reductase, which remains to be identified, could have a minor effect on the reduction of methemoglobin.

RCM type 1 is caused by mutations of the CYB5R3 gene (22q13.31-qter) encoding the NADH-cytochrome b5 reductase (Cb5R) and Cb5R deficiency is limited to the erythrocytes. RCM type 2 is caused by global loss of Cb5R function. Over 40 different CYB5R3 mutations have been identified so far, some of which have been identified in both types. RCM type 1 is generally associated with missense mutations, whereas RCM type 2 is more commonly associated with truncating mutations, splicing errors or mutations that lead to disruption of the active site.

Management and treatment
Treatment of methemoglobinemia revolves around administration of methylene blue and/or ascorbic acid. Although ascorbic acid alone is sufficient to alleviate the cyanosis in milder cases, the reaction rate is slower than that of the combined treatment. However, these treatments have no effect on the neurological dysfunction in RCM type 2.

Visit the Orphanet disease page for more resources.


This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
80%-99% of people have these symptoms
Blue discoloration of the skin
30%-79% of people have these symptoms
Abnormality of the nail
Exertional dyspnea
Lip discoloration
5%-29% of people have these symptoms
Involuntary writhing movements in fingers, hands, toes, and feet
Blue sclerae
Whites of eyes are a bluish-gray color
Cerebellar atrophy
Degeneration of cerebellum
Cerebral hypomyelination
Inward turning cross eyed
Frontal cortical atrophy
Global brain atrophy
Generalized brain degeneration
Intellectual disability, severe
Early and severe mental retardation
Mental retardation, severe
Severe mental retardation

[ more ]

Limb dystonia
Abnormally small skull
Decreased circumference of cranium
Decreased size of skull
Reduced head circumference
Small head circumference

[ more ]

Severe global developmental delay
Spastic tetraplegia
Temporal cortical atrophy
1%-4% of people have these symptoms
Delayed myelination
Small basal ganglia
Small for gestational age
Birth weight less than 10th percentile
Low birth weight

[ more ]


Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
  • Genetics Home Reference (GHR) contains information on Hereditary methemoglobinemia. This website is maintained by the National Library of Medicine.

In-Depth Information

  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.