Differential Diagnosis for Infectious Disease with Lower Extremity Rash and Sepsis
- Single most likely diagnosis
- Necrotizing Fasciitis: This condition is characterized by a severe infection of the skin and underlying tissues, often starting in the lower extremities. It can rapidly progress to sepsis and is known for its high mortality rate if not promptly treated. The presence of a rash, severe pain, and signs of sepsis make necrotizing fasciitis a leading consideration.
- Other Likely diagnoses
- Cellulitis with Sepsis: Cellulitis is a common bacterial skin infection that can spread and lead to sepsis, especially if not treated promptly. It typically presents with redness, swelling, and warmth of the skin, often on the lower extremities.
- Erysipelas: This is a type of skin infection that involves the upper dermis, typically caused by beta-hemolytic group A Streptococcus. It presents with a well-demarcated, raised, and shiny rash, often accompanied by systemic symptoms such as fever and can progress to sepsis.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Meningococcemia: Although less common, meningococcemia is a severe infection caused by Neisseria meningitidis that can present with a rash (petechiae or purpura) and rapidly progress to sepsis and meningitis. It is critical to consider this diagnosis due to its high mortality rate if not promptly treated.
- Rocky Mountain Spotted Fever (RMSF): This tick-borne illness, caused by Rickettsia rickettsii, can present with a rash (often starting on the wrists and ankles) and fever, progressing to sepsis. It is essential to consider RMSF in patients with a history of tick exposure.
- Rare diagnoses
- Anthrax: Cutaneous anthrax can present with a skin lesion that progresses to a black eschar, and in rare cases, it can lead to sepsis. Although rare, anthrax is a consideration in individuals with exposure to animals or contaminated animal products.
- Rickettsialpox: Caused by Rickettsia akari, this disease is transmitted by the bite of an infected mite and can present with a rash and systemic symptoms, including fever and headache. It is rare but should be considered in the appropriate epidemiological context.