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GTR Home > Conditions/Phenotypes > Methemoglobinemia type 4

Methemoglobinemia type 4

Synonyms
METHEMOGLOBINEMIA DUE TO DEFICIENCY OF CYTOCHROME b5

Summary

Methemoglobinemia and ambiguous genitalia (METAG) is due to isolated 17,20-lyase deficiency, defined by apparently normal 17-alpha-hydroxylase activity but severely reduced 17,20-lyase activity of the CYP17A1 enzyme (609300), which results in sex steroid deficiency but normal glucocorticoid and mineralocorticoid reserve. The clinical phenotype is characterized by male undermasculinization, with absent or disturbed pubertal development in both 46,XY and 46,XX individuals. Mild to severe methemoglobinemia has been reported in these patients (Idkowiak et al., 2012). Other autosomal recessive methemoglobinemias include types I and II (see 250800), caused by mutation in the CYB5R3 gene (613213). Isolated 17,20-lyase deficiency can also be caused by mutation in the CYP17A1 gene (609300), and mutation in the POR gene can manifest clinically as isolated 17,20-lyase deficiency (see 124015.0016). [from OMIM]

Available tests

18 tests are in the database for this condition.

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Clinical tests (18 available)

Molecular Genetics Tests

Genes See tests for all associated and related genes

  • Also known as: CYB5, MCB5, METAG, CYB5A
    Summary: cytochrome b5 type A

Clinical features

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Imported from Human Phenotype Ontology (HPO)

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