Differential Diagnosis for Fever Followed by Rash
- Single most likely diagnosis
- Viral Exanthem (e.g., Roseola): This is a common condition in children, characterized by a high fever that lasts for a few days, followed by a rash that appears once the fever resolves. The rash is typically pink, blanching, and maculopapular.
- Other Likely diagnoses
- Measles: Although less common in areas with high vaccination rates, measles starts with fever, followed by the three Cs: cough, coryza (runny nose), and conjunctivitis, and then a rash. The rash in measles is more confluent and starts on the face.
- Scarlet Fever: Caused by Group A beta-hemolytic streptococci, it presents with fever, sore throat, and then a rash that feels like sandpaper. The rash typically starts on the trunk and spreads.
- Kawasaki Disease: An acute febrile illness of childhood, characterized by fever, rash, conjunctivitis, cervical lymphadenopathy, and changes in the lips and oral cavity. It's a leading cause of acquired heart disease in children.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Meningococcemia: A severe infection caused by Neisseria meningitidis, presenting with fever, rash (petechial or purpuric), and potentially life-threatening if not treated promptly. The rash does not blanch under pressure.
- Rocky Mountain Spotted Fever (RMSF): A tick-borne disease caused by Rickettsia rickettsii, characterized by fever, headache, and a rash that appears 2-5 days after the onset of fever. The rash is typically petechial and starts on the wrists and ankles.
- Toxic Shock Syndrome: A medical emergency caused by bacterial toxins, often presenting with fever, rash, hypotension, and involvement of three or more organ systems. The rash can be diffuse and maculopapular.
- Rare diagnoses
- Erythema Infectiosum (Fifth Disease): Caused by Parvovirus B19, it presents with a "slapped-cheek" appearance followed by a lacy rash on the body. It's usually mild but can be more severe in immunocompromised individuals.
- Dengue Fever: A mosquito-borne viral illness common in tropical and subtropical climates, characterized by high fever, severe headache, and a rash that appears 2-5 days after the onset of fever. It can progress to severe forms like Dengue Hemorrhagic Fever.