Differential Diagnosis for 16-month-old with Fever and Rash

• Single most likely diagnosis
  • Roseola infantum: This is a common illness in children under 2 years, characterized by a high fever that lasts for 3-5 days, followed by a rash that appears as the fever resolves. The rash typically starts on the trunk and spreads to other parts of the body.
• Other Likely diagnoses
  • Viral exanthem (e.g., measles, rubella, or enterovirus): These viral infections can cause fever and rash in children, although the specific characteristics of the rash and accompanying symptoms can vary.
  • Scarlet fever: Caused by Group A beta-hemolytic streptococci, this condition presents with a distinctive rash that feels like sandpaper, fever, and other symptoms like a strawberry tongue.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Meningococcemia: Although less common, this bacterial infection can cause fever, rash, and severe illness. The rash can start as small, pink spots that turn into purple blotches, and it's critical to identify and treat promptly due to the risk of sepsis and meningitis.
  • Kawasaki disease: An acute febrile illness of childhood that can lead to coronary artery aneurysms if not treated. It presents with fever, rash, conjunctivitis, cervical lymphadenopathy, and changes to the lips and oral cavity.
• Rare diagnoses
  • Juvenile idiopathic arthritis (JIA): Systemic JIA can present with fever and rash, although it's less common in this age group and typically accompanied by joint symptoms.
  • Leukemia: Certain types of leukemia can cause fever and rash, among other symptoms, due to bone marrow infiltration and immune system dysfunction.