Differential Diagnosis for Multiple Oral Ulcers without Rash on Hands and Feet

Single Most Likely Diagnosis

• Herpangina: This condition is characterized by the presence of multiple small, painful ulcers in the mouth, often without a rash on the hands and feet. It's commonly caused by Coxsackieviruses, which are also responsible for Hand, Foot, and Mouth Disease (HFMD), but herpangina typically lacks the characteristic rash on extremities.

Other Likely Diagnoses

• Aphthous Ulcers: These are common, recurrent, and can appear as multiple ulcers in the mouth. They are not typically associated with systemic illnesses like HFMD but can cause significant discomfort.
• Oral Ulcers due to Viral Infections (e.g., HSV, CMV): Various viral infections can cause oral ulcers. While some, like HSV, might also cause lesions on the lips or around the mouth, others might not have additional symptoms like rash on hands and feet.
• Traumatic Ulcers: Accidental bites, sharp edges of teeth, or other oral trauma can cause ulcers. These would be localized to the area of injury and not part of a systemic illness.

Do Not Miss Diagnoses

• Hand, Foot, and Mouth Disease (HFMD) with Atypical Presentation: Although HFMD typically presents with a rash on the hands and feet, there can be atypical cases where the rash is minimal or absent. Given the overlap in causative viruses with herpangina, it's crucial not to rule out HFMD solely based on the absence of a rash.
• Steven-Johnson Syndrome/Toxic Epidermal Necrolysis: These are severe skin and mucous membrane disorders, usually a reaction to medication or infection. Oral ulcers can be a part of the presentation, and while a rash is a key feature, the condition's severity and potential for significant morbidity make it a "do not miss" diagnosis.

Rare Diagnoses

• Behçet's Disease: A form of vasculitis that can cause oral ulcers, among other symptoms. It's less common and typically presents with a combination of oral ulcers, genital ulcers, and ocular inflammation.
• Pemphigus Vulgaris: An autoimmune disease causing blistering of the skin and mucous membranes. Oral ulcers can be the first sign, but it's a rare condition.
• Erythema Multiforme: An immune-mediated disorder that can cause oral ulcers and skin lesions. It's relatively rare and often triggered by infections or medications.

Each of these diagnoses has distinct features, but the presence of multiple oral ulcers without a rash on the hands and feet necessitates a careful evaluation to determine the underlying cause.