Differential Diagnosis for a 4-year-old Female Toddler with Intermittent Rash and Small Bite-like Bumps

• Single most likely diagnosis:
  • Insect Bite Reaction: This is the most likely diagnosis given the description of small bite-like bumps without any reported bites. It's common for young children to react to insect bites with such symptoms, and the lack of reported bites doesn't rule out the possibility since they might have occurred unnoticed.
• Other Likely diagnoses:
  • Eczema (Atopic Dermatitis): Could present with itchy, small bumps, although it typically has a more chronic course and is associated with other symptoms like dry skin.
  • Contact Dermatitis: An allergic reaction to something that has come into contact with the skin, which could cause a rash and small bumps.
  • Urticaria (Hives): Although hives are typically larger and more transient, some forms can present with smaller lesions.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Meningococcemia: A severe infection that can cause a rash, which might initially resemble small bumps or bites. It's critical to consider this diagnosis due to its high mortality rate if not promptly treated.
  • Rocky Mountain Spotted Fever (RMSF): A tick-borne illness that can present with a rash, which might initially look like small bumps or bites, and is severe if not treated early.
• Rare diagnoses:
  • Sweet Syndrome (Acute Febrile Neutrophilic Dermatosis): Characterized by fever, leukocytosis, and tender, erythematous skin lesions, which could be mistaken for bite-like bumps in some cases.
  • Erythema Multiforme: An immune-mediated disorder that can cause skin lesions, which might resemble small bumps or target lesions, often associated with viral infections or medications.