Differential Diagnosis for Green Discoloration on the Inside of the Mouth

• Single Most Likely Diagnosis
  • Oral candidiasis (thrush): This is a common fungal infection that can cause white or greenish patches on the mucous membranes of the mouth, including the inside of the cheeks and tongue. The green color could be due to the presence of secondary bacterial infections or the patient's oral hygiene.
• Other Likely Diagnoses
  • Poor oral hygiene: Accumulation of bacteria, dead cells, and debris can cause green or yellowish discoloration on the teeth, tongue, and inside of the mouth.
  • Tobacco use: Tobacco can cause greenish or brownish stains on the teeth and mucous membranes due to the accumulation of tar and other chemicals.
  • Dental problems: Abscesses, infected gums, or dental caries can cause greenish or yellowish discharge or discoloration in the mouth.
• Do Not Miss Diagnoses
  • Oral cancer: Although less likely, oral cancer can cause unusual discoloration, including greenish patches, especially if there is an associated infection or necrosis. It is crucial to rule out this diagnosis due to its severe consequences.
  • Infectious diseases (e.g., herpes, syphilis): Certain infectious diseases can cause oral lesions or discoloration, including greenish patches, and it is essential to consider these diagnoses to provide appropriate treatment.
• Rare Diagnoses
  • Oral melanin pigmentation: This is a rare condition that can cause greenish or bluish discoloration on the mucous membranes due to the accumulation of melanin.
  • Lichen planus: A chronic autoimmune condition that can cause white, greenish, or bluish patches on the mucous membranes, although the green color is less common.
  • Medication side effects: Certain medications, such as those used for cancer treatment or antipsychotics, can cause oral discoloration, including greenish patches, as a rare side effect.