Differential Diagnosis for Viral Rash Starting in Extremities and Spreading to Torso

• Single Most Likely Diagnosis
  • Hand, Foot, and Mouth Disease (HFMD): This is a common viral illness that typically starts with sores in the mouth and a rash on the hands and feet, then can spread to other areas including the torso. It's highly contagious and often seen in children.
• Other Likely Diagnoses
  • Measles: Although vaccination has made measles less common, it still occurs. The rash in measles starts on the face and then spreads to the rest of the body, including the extremities and torso. However, the initial presentation often includes high fever, cough, runny nose, and conjunctivitis.
  • Rubella (German Measles): Similar to measles, rubella starts on the face and spreads downward. It's characterized by a low-grade fever, sore throat, and the rash.
• Do Not Miss Diagnoses
  • Monkeypox: A rare disease that can present with a rash starting on the face and spreading to other parts of the body, including the extremities and torso. Given its potential for severe illness and the current global health situation, it's crucial not to miss this diagnosis.
  • Smallpox: Although eradicated, in the event of a bioterrorism attack, smallpox could re-emerge. The rash starts in the mouth and throat and then spreads to the face, arms, and legs, and finally to the torso. It's characterized by a uniform progression of rash stages.
• Rare Diagnoses
  • Dengue Fever: While primarily known for its fever and severe flu-like symptoms, dengue can sometimes present with a rash. The rash can appear early in the course of the disease and may start on the extremities before spreading.
  • Chikungunya: This viral disease is characterized by fever and severe joint pain, and it can also present with a rash. The rash may start on the trunk and spread to the limbs, but variations in presentation can occur.