What is the cause of a rash in a man after rescuing his cat from bushes, suspected to be a Type 4 hypersensitivity (delayed hypersensitivity) reaction?

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Last updated: March 28, 2025View editorial policy

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Differential Diagnosis for Rash after Rescuing Cat from Bushes

Single most likely diagnosis

  • Cat scratch disease: This is the most likely diagnosis due to the direct contact with the cat, which can transmit the bacterium Bartonella henselae through scratches or bites, leading to a type 4 hypersensitivity reaction and subsequent rash.

Other Likely diagnoses

  • Contact dermatitis: Exposure to plants or other allergens in the bushes could cause an allergic reaction, resulting in a rash.
  • Flea bites: If the cat had fleas, the man could have been bitten while rescuing the cat, leading to an allergic reaction and rash.
  • Insect bites or stings: Other insects in the bushes, such as mosquitoes, bees, or wasps, could have bitten or stung the man, causing a rash.

Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)

  • Rabies: Although rare, if the cat is infected with rabies, the man could be at risk of transmission through scratches or bites.
  • Tetanus: If the man has an open wound from the rescue and has not received a recent tetanus shot, he may be at risk of tetanus infection.
  • Lyme disease: If the cat had ticks, the man could be at risk of Lyme disease transmission, which can cause a rash and other systemic symptoms.

Rare diagnoses

  • Erythema migrans: A rash caused by the bacterium Borrelia burgdorferi, transmitted through tick bites, which can be found on cats.
  • Leptospirosis: A bacterial infection that can be transmitted through contact with infected animal urine, which could be present in the bushes.
  • Capnocytophaga: A bacterial infection that can be transmitted through cat bites or scratches, which can cause a rash and other systemic symptoms.

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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