Differential Diagnosis for a Rash Appearing After Fever
- Single Most Likely Diagnosis
- Roseola: This is a common illness in children, characterized by a high fever followed by a rash. The rash typically appears after the fever has resolved, making it a likely diagnosis for a rash appearing after fever.
- Other Likely Diagnoses
- Measles: Although vaccination has made measles less common, it still occurs and is characterized by a fever, cough, runny nose, and a rash that appears a few days after the onset of fever.
- Rubella (German Measles): Similar to measles, rubella is a viral infection that causes a fever and rash, although the rash in rubella tends to be milder and may appear simultaneously with or after the fever.
- Scarlet Fever: Caused by Group A beta-hemolytic streptococci, this condition is marked by a high fever, sore throat, and a rash that appears 1-2 days after the onset of fever.
- Do Not Miss Diagnoses
- Meningococcemia: This is a severe infection caused by Neisseria meningitidis, which can present with fever and a rash. The rash can be petechial or purpuric and is a medical emergency due to the risk of sepsis and meningitis.
- Rocky Mountain Spotted Fever (RMSF): A tick-borne illness caused by Rickettsia rickettsii, RMSF is characterized by fever, headache, and a rash that typically appears 2-5 days after the onset of fever. It is critical to diagnose and treat promptly to prevent serious complications.
- Rare Diagnoses
- Kawasaki Disease: An acute febrile illness of childhood, Kawasaki disease is characterized by fever, rash, conjunctivitis, and changes to the lips and oral cavity. It is rare but important to consider due to the risk of coronary artery aneurysms if not treated.
- Erythema Infectiosum (Fifth Disease): Caused by parvovirus B19, this illness is more common in children and is known for its "slapped cheek" appearance, followed by a lacy rash on the body. It usually starts with a fever.