What is the diagnosis for a patient presenting with an infectious disease, lower extremity rash, and signs of sepsis (Systemic Inflammatory Response Syndrome)?

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DS

Dainyal Siddiqui, MD

Internal Medicine

MJ

Manuel Jimenez, MD

Cardiology

FP

Franz Pierre-Louis, MD

Infectious Disease

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Last updated: April 6, 2025 • View editorial policy

Differential Diagnosis for Infectious Disease with Lower Extremity Rash and Sepsis

Single Most Likely Diagnosis

  • Cellulitis: This is a common bacterial skin infection that can cause redness, swelling, and warmth of the skin, often accompanied by systemic symptoms such as fever and sepsis. The presence of a lower extremity rash and sepsis makes cellulitis a highly plausible diagnosis.

Other Likely Diagnoses

  • Erysipelas: A type of bacterial infection of the upper layer of the skin that can cause a well-defined, raised, and tender rash, often on the lower extremities. It can lead to sepsis if not treated promptly.
  • Necrotizing Fasciitis: A severe infection of the tissue beneath the skin and surrounding muscles and nerves, which can cause pain, swelling, and rash. It is a medical emergency and can lead to sepsis and death if not treated aggressively.
  • Staphylococcal Scalded Skin Syndrome (SSSS): Caused by staphylococcal toxins, SSSS leads to widespread skin lesions and can cause sepsis, especially in children and immunocompromised individuals.

Do Not Miss Diagnoses

  • Meningococcemia: A severe infection caused by Neisseria meningitidis, which can present with a rash, fever, and sepsis. It is critical to diagnose and treat promptly due to its high mortality rate.
  • Rocky Mountain Spotted Fever (RMSF): A tick-borne illness caused by Rickettsia rickettsii, characterized by fever, headache, and a rash that can progress to sepsis and death if not treated early.
  • Toxic Shock Syndrome (TSS): Caused by bacterial toxins, TSS can present with fever, rash, and sepsis, and is a medical emergency requiring immediate treatment.

Rare Diagnoses

  • Leptospirosis: A zoonotic infection caused by Leptospira bacteria, which can cause a wide range of symptoms including rash, fever, and sepsis, especially in individuals who have been exposed to contaminated water.
  • Rickettsialpox: A rare disease caused by Rickettsia akari, transmitted by the bite of an infected mite, which can cause a rash, fever, and sepsis.
  • Anthrax: A rare but potentially deadly infection caused by Bacillus anthracis, which can cause a skin lesion that progresses to sepsis if not treated.

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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