Purple Tongue: Cyanosis as a Medical Emergency

A purple tongue indicates **central cyanosis** — deoxygenated hemoglobin >5 g/dL in capillary blood. This is a sign of significant hypoxemia requiring urgent evaluation.

Causes of Central Cyanosis

• Cardiac: Right-to-left shunt (Eisenmenger, Tetralogy of Fallot), acute heart failure, pulmonary embolism, congenital heart disease.
• Pulmonary: Severe COPD exacerbation, pneumonia, ARDS, pulmonary edema, severe asthma, high altitude.
• Hematologic: Methemoglobinemia (oxidized Hb — chocolate cyanosis unresponsive to O₂), sulfhemoglobinemia.
• Toxic: Carbon monoxide poisoning (cherry red, but can appear dusky), cyanide.
• Neuromuscular: Hypoventilation (Guillain-Barré, myasthenia, opioid overdose).

Peripheral vs. Central Cyanosis

• Central: Tongue, lips, oral mucosa — reflects arterial hypoxemia.
• Peripheral: Fingers, toes, nose — vasoconstriction, slow flow; tongue pink.

Immediate Actions

1. Assess ABCs; apply supplemental O₂.
2. Pulse oximetry (may be falsely normal in methemoglobinemia — co-oximetry needed).
3. ABG with co-oximetry (Hb species).
4. ECG, CXR, CT angiography per suspicion.
5. Methylene blue for methemoglobinemia.

Non-Cyanotic Purple Tongue

Rare: lingual varices, Kaposi sarcoma, trauma, pigmented lesions — but **always rule out cyanosis first**.