Central cyanosis
More common causes
Hypothermia
Obstructive sleep apnea
Altitude sickness
Less common causes
Pulmonary valve stenosis
Polycythemia
Respiratory failure
Tricuspid valve stenosis
Methemoglobinemia
Eisenmenger syndrome
Right-to-left shunt
Hypoxemic respiratory failure
Pseudocyanosis
Uncommon causes
Sulfhemoglobinemia