Differential Diagnosis for Herpes Keratitis in a 10-Year-Old with Rapidly Spreading Rash

• Single Most Likely Diagnosis
  • Herpes Simplex Virus (HSV) infection: This is the most likely diagnosis given the presentation of herpes keratitis, which is often caused by HSV. The rapidly spreading rash could be indicative of a disseminated or severe HSV infection, particularly in an immunocompetent child.
• Other Likely Diagnoses
  • Varicella-Zoster Virus (VZV) infection: Although less common as a cause of keratitis compared to HSV, VZV can cause a rash and, if the child has had chickenpox, could reactivate as herpes zoster (shingles), potentially involving the eye.
  • Epstein-Barr Virus (EBV) infection: While EBV is more commonly associated with infectious mononucleosis, it can cause a range of symptoms including rash and, in rare cases, ocular manifestations.
• Do Not Miss Diagnoses
  • Eczema Herpeticum: A potentially life-threatening complication of atopic dermatitis (eczema) caused by HSV or, less commonly, coxsackievirus A16. It presents with a rapidly spreading, painful rash and can lead to serious complications if not promptly treated.
  • Stevens-Johnson Syndrome (SJS) or Toxic Epidermal Necrolysis (TEN): These are severe skin and mucous membrane disorders, usually a reaction to medication or infection. They can present with a rash and ocular involvement, including keratitis, and are medical emergencies.
• Rare Diagnoses
  • Cytomegalovirus (CMV) retinitis: More commonly seen in immunocompromised patients, CMV can cause ocular disease, but it's less likely to present with a rapidly spreading rash.
  • Enteroviral infections: Certain enteroviruses can cause a range of symptoms including rash and, in rare cases, ocular manifestations, but they are less commonly associated with keratitis compared to HSV or VZV.