Herpes Simplex Virus (HSV) infection: This is the most common cause of herpetic gingivostomatitis, characterized by painful ulcers and inflammation of the gums and oral mucosa, often accompanied by fever and irritability in children.

Hand, Foot, and Mouth Disease (HFMD): Caused by Coxsackievirus A or Enterovirus 71, presenting with similar oral ulcers and vesicles on the hands and feet.
Aphthous Stomatitis: Recurring ulcers in the oral cavity, though typically less severe and without the systemic symptoms seen in herpetic gingivostomatitis.
Acute Necrotizing Ulcerative Gingivitis (ANUG): A condition characterized by painful, bleeding gums and ulcers, often associated with stress, poor oral hygiene, or immunosuppression.

Primary HIV Infection: Can present with oral ulcers and systemic symptoms similar to herpetic gingivostomatitis, making it crucial for diagnosis due to the significant implications of HIV infection.
Stevens-Johnson Syndrome: A severe skin and mucous membrane disorder, usually a reaction to medication or infection, which can present with oral ulcers and requires immediate medical attention.
Autoimmune Disorders (e.g., Pemphigus Vulgaris): Conditions that can cause oral ulcers and require specific treatment to prevent serious complications.

Behçet's Disease: A rare disorder that causes blood vessel inflammation throughout the body and can present with oral ulcers, among other symptoms.
Erythema Multiforme: An immune-mediated condition that can cause oral ulcers and skin lesions, often in response to infections or medications.
Kawasaki Disease: Although primarily known for its presentation in children with fever, rash, and lymphadenopathy, it can also cause oral mucosal changes and should be considered in the appropriate clinical context.