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Last updated: September 20, 2025View editorial policy

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Differential Diagnosis

  • Single most likely diagnosis
    • Oral candidiasis (thrush): This is a common condition that can cause visible lesions inside the mouth, particularly on one side. It's more likely to be visible in normal lighting and with a handheld pen light, and it often presents unilaterally.
  • Other Likely diagnoses
    • Mucosal trauma or ulcer: Trauma to the mucous membranes inside the mouth can cause visible lesions or ulcers, which could be seen on one side of the mouth.
    • Aphthous ulcers: These are small, painful ulcers that can appear inside the mouth, often on one side, and can be visible with normal lighting.
    • Leukoplakia: This is a condition where thick, white patches or lesions form on the mucous membranes inside the mouth, which could be visible on one side.
  • Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
    • Oral cancer: Although less likely, oral cancer can present as a visible lesion inside the mouth and is crucial to diagnose early. It may appear as a white patch, red patch, or an ulcer, and can be located on one side of the mouth.
    • Tuberculosis (TB) of the oral cavity: TB can cause lesions or ulcers in the mouth, which might be visible on one side. Given the potential severity of TB, it's essential not to miss this diagnosis.
  • Rare diagnoses
    • Lichen planus: This is a rare condition that can cause white, lacy patches or lesions inside the mouth, which might be visible on one side.
    • Pemphigus: A group of rare skin disorders that can cause blisters or lesions inside the mouth, potentially visible on one side.
    • Histoplasmosis: A fungal infection that can cause lesions or ulcers in the mouth, particularly in immunocompromised individuals, and might be visible on one side of the mouth.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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