Differential Diagnosis for Popular Rash after Febrile Illness

• Single most likely diagnosis
  • Roseola: A common illness in children characterized by a high fever followed by a rash, making it a likely candidate given the symptoms.
• Other Likely diagnoses
  • Scarlet fever: Although less common, it can present with a rash after a febrile illness, especially if associated with a streptococcal infection.
  • Measles: Despite vaccination efforts, measles can still occur and presents with fever, rash, and other systemic symptoms.
  • Rubella: Similar to measles, rubella (German measles) is characterized by a rash following a febrile illness.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Meningococcemia: A severe, potentially life-threatening infection that can cause a rash, fever, and rapidly progress to sepsis or meningitis.
  • Rocky Mountain Spotted Fever (RMSF): A tick-borne illness that can present with fever and rash, and is critical to diagnose early due to its potential severity.
  • Toxic Shock Syndrome: A condition that can arise from bacterial infections, characterized by fever, rash, and potentially life-threatening complications.
• Rare diagnoses
  • Kawasaki Disease: An illness that mainly affects children, causing fever, rash, and other symptoms, with potential for serious cardiac complications if not treated.
  • Erythema Infectiosum (Fifth Disease): Caused by parvovirus B19, it leads to a distinctive "slapped cheek" rash and can be accompanied by fever, though it's generally mild.
  • Enteroviral infections: Certain enteroviruses can cause rashes and febrile illnesses, though they are less commonly identified as the cause compared to other viral rashes.