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 can be due to certain medications, chemicals, or food or it can be inherited from a persons parents. Substances involved may include benzocaine, nitrates, 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. Signs and symptoms
Signs and symptoms of methemoglobinemia (methemoglobin level above 10%) include shortness of breath, cyanosis, mental status changes (~50%), headache, fatigue, exercise intolerance, dizziness, and loss of consciousness.People with severe methemoglobinemia (methemoglobin level above 50%) may exhibit seizures, coma, and death (level above 70%). Healthy people may not have many symptoms with methemoglobin levels below 15%. However, people with co-morbidities such as anemia, cardiovascular disease, lung disease, sepsis, or who have abnormal hemoglobin species (e.g. carboxyhemoglobin, sulfhemoglobinemia or sickle hemoglobin) may experience moderate to severe symptoms at much lower levels (as low as 5–8%). Cause
Acquired
Methemoglobinemia may be acquired.
Genital ambiguities are frequently detected during clinical examination at birth, and consequently, a PAIS diagnosis can be made during infancy as part of a differential diagnostic workup.Pubertal undervirilization is common, including gynecomastia, decreased secondary terminal hair, and / or a high pitched voice. The phallic structure ranges from a penis with varying degrees of diminished size and hypospadias to a slightly enlarged clitoris. Wolffian structures (the epididymides, vasa deferentia, and seminal vesicles) are typically partially or fully developed. The prostate is typically small or impalpable. Müllerian remnants are rare, but have been reported.The gonads in individuals with PAIS are testes, regardless of phenotype; during the embryonic stage of development, testes form in an androgen-independent process that occurs due to the influence of the SRY gene on the Y chromosome. Cryptorchidism is common, and carries with it a 50% risk of germ cell malignancy. If the testes are located intrascrotally, there may still be significant risk of germ cell malignancy; studies have not yet been published to assess this risk.Predominantly male phenotypes vary in the degree of genital undermasculinization to include micropenis, chordee, bifid scrotum, and / or pseudovaginal perineoscrotal hypospadias. Impotence may be fairly common, depending on phenotypic features; in one study of 15 males with PAIS, 80% of those interviewed indicated that they had some degree of impotence. Anejaculation appears to occur somewhat independently of impotence; some men are still able to ejaculate despite impotence, and others without erectile difficulties cannot. Predominantly female phenotypes include a variable degree of labial fusion and clitoromegaly.