Differential Diagnosis for 15-month-old Male with Rash

• Single most likely diagnosis
  • Amoxicillin-induced rash: This is a common adverse reaction to amoxicillin, especially in children. The rash typically appears 3-10 days after starting the antibiotic, which aligns with the patient's timeline.
• Other Likely diagnoses
  • Viral exanthem: Given the patient's recent history of hand-foot-and-mouth disease, another viral exanthem is possible. The rash could be a manifestation of a different viral infection.
  • Allergic contact dermatitis: Although less likely, the patient could have developed an allergic reaction to something in his environment, such as a soap or lotion.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Stevens-Johnson syndrome (SJS) or Toxic Epidermal Necrolysis (TEN): Although rare, these conditions are life-threatening and can be triggered by medications like amoxicillin. Early recognition is crucial for prompt treatment.
  • Bacterial sepsis: If the patient's rash is a sign of a more severe infection, such as sepsis, it would be critical to identify and treat promptly.
• Rare diagnoses
  • Kawasaki disease: This condition is characterized by a rash, fever, and other symptoms. Although rare, it's essential to consider in the differential diagnosis, especially if the patient has other symptoms like fever or lymphadenopathy.
  • Serum sickness-like reaction: This is a rare condition that can occur after taking certain medications, including amoxicillin. It's characterized by a rash, fever, and other symptoms.