Conclusion:
Due to mild symptoms, congenital methemoglobinemia is rarely diagnosed
and reported as a cause of the cyanosis, especially in adults. Despite
the benign nature of congenital methemoglobinemia, it is crucial to keep
it in the differential diagnosis list when assessing cyanotic patients,
mainly if he has a normal PaO2. Patients are usually asymptomatic and
are treated for cosmetic purposes, but they might suffer from severe
complications if exposed to oxidative agents.
In summary, congenital methemoglobinemia is a rare but treatable cause
of cyanosis that should be considered in the differential diagnosis of
cyanosis.