Differential Diagnosis for Bluish Blackening of Tongue

• Single most likely diagnosis
  • Post-mortem lividity or hypostasis: This is the most common cause of bluish blackening of the tongue, occurring after death due to the settling of blood in the dependent parts of the body.
• Other Likely diagnoses
  • Cyanide poisoning: Cyanide can cause a rapid onset of symptoms, including a bluish discoloration of the skin and mucous membranes, due to its effect on cellular respiration.
  • Carbon monoxide poisoning: Similar to cyanide, carbon monoxide can lead to tissue hypoxia, resulting in a bluish discoloration.
  • Methemoglobinemia: This condition, caused by certain medications or toxins, leads to an abnormal amount of methemoglobin in the blood, which cannot effectively release oxygen to tissues, resulting in a cyanotic appearance.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Sulfhemoglobinemia: A rare condition where sulfhemoglobin is present in the blood, leading to a particular type of cyanosis that is resistant to oxygen therapy. It's crucial to identify this condition due to its implications for treatment.
  • Acute respiratory distress syndrome (ARDS) with severe hypoxemia: While not directly causing a bluish blackening of the tongue, severe hypoxemia can lead to cyanosis, and ARDS is a life-threatening condition requiring immediate intervention.
• Rare diagnoses
  • Arginine or nitrate poisoning: These can lead to methemoglobinemia, but are less common causes.
  • Certain infections (e.g., gangrenous stomatitis): Though rare, certain infections can cause necrosis and discoloration of the tongue.
  • Congenital methemoglobinemia: A rare genetic disorder affecting the production of certain enzymes, leading to elevated levels of methemoglobin.