Differential Diagnosis for Rash in Buccal Mucosa

• Single most likely diagnosis
  • Stevens-Johnson Syndrome (SJS)/Toxic Epidermal Necrolysis (TEN): This condition is characterized by a severe skin and mucous membrane disorder, usually caused by an adverse reaction to medications. The presence of a rash in the buccal mucosa, along with skin lesions, makes SJS/TEN a highly probable diagnosis.
• Other Likely diagnoses
  • Erythema Multiforme (EM): A skin condition characterized by target lesions, often involving the mucous membranes. It can be triggered by infections or medications, making it a plausible diagnosis for a rash in the buccal mucosa.
  • Pemphigus Vulgaris: An autoimmune disease causing blistering of the skin and mucous membranes. The buccal mucosa is often involved, making it a likely consideration.
  • Lichen Planus: A chronic inflammatory condition that can affect the skin, mouth, and other areas. Oral lichen planus can cause lesions in the buccal mucosa, among other symptoms.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Primary Herpetic Gingivostomatitis: Although more common in children, this condition can cause severe oral lesions and should not be overlooked due to its potential for significant morbidity.
  • Cancer (e.g., Squamous Cell Carcinoma): Although less likely, any persistent or unusual lesion in the buccal mucosa could be a sign of oral cancer, making it crucial not to miss this diagnosis.
• Rare diagnoses
  • Paraneoplastic Pemphigus: A rare autoimmune disorder associated with underlying neoplasia, characterized by severe mucocutaneous blistering.
  • Mucous Membrane Pemphigoid: A group of rare chronic autoimmune diseases characterized by blistering lesions of the mucous membranes, including the buccal mucosa.