Differential Diagnosis for Confusion and Rash Starting with Feet and Spreading Upwards

• Single most likely diagnosis:
  • Toxic Epidermal Necrolysis (TEN) or Stevens-Johnson Syndrome (SJS): These conditions are characterized by a severe skin and mucous membrane disorder, usually caused by medications. The symptoms can start with the feet and spread upwards, accompanied by confusion due to the systemic nature of the disease.
• Other Likely diagnoses:
  • Erythema Multiforme: An immune-mediated skin condition that can present with a rash starting on the extremities, including the feet, and can be accompanied by systemic symptoms such as confusion in severe cases.
  • Infectious Diseases (e.g., Rocky Mountain Spotted Fever, Lyme Disease): Certain infections can cause a rash that starts on the extremities and spreads, along with systemic symptoms like confusion due to the infection itself or the body's response to it.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed):
  • Meningococcemia: A severe infection caused by Neisseria meningitidis, which can present with a rash (often starting on the feet) and confusion due to meningitis or sepsis. It is critical to identify and treat promptly due to its high mortality rate.
  • Toxic Shock Syndrome: Caused by bacterial toxins, this condition can lead to a rash, confusion, and multi-organ failure. Early recognition and treatment are crucial for survival.
• Rare diagnoses:
  • Kawasaki Disease: Although more common in children, it can cause a rash, fever, and systemic symptoms including confusion. The rash can start on the feet, but it's less common in adults.
  • Leptospirosis: A zoonotic infection that can cause a wide range of symptoms, including a rash and confusion. The rash might start on the feet in some cases, but it's relatively rare and often associated with exposure to contaminated water.