Differential Diagnosis for Cat Scratch in Infant

• Single most likely diagnosis
  • Cat scratch disease (Bartonellosis): This is the most likely diagnosis due to the direct exposure to a cat scratch, which is a common mode of transmission for Bartonella henselae, the bacterium responsible for cat scratch disease.
• Other Likely diagnoses
  • Cellulitis: A bacterial infection of the skin and subcutaneous tissues, which could be caused by various bacteria introduced through the scratch.
  • Abscess: A localized collection of pus that can form as a result of a bacterial infection following a cat scratch.
  • Folliculitis: An inflammation of the hair follicles, which can occur after a cat scratch, especially if the scratch becomes infected.
• 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, a scratch could potentially transmit the virus, making prompt identification and treatment critical.
  • Tetanus: A bacterial infection characterized by muscle spasms, which can be introduced through wounds, including scratches, if the infant is not up to date on tetanus vaccinations.
  • Bacterial endocarditis: In rare cases, bacteria introduced through a scratch could lead to an infection of the heart valves, particularly in infants with pre-existing heart conditions.
• Rare diagnoses
  • Pasteurella multocida infection: A bacterium commonly found in the mouths of cats and dogs, which can cause infections in humans through bites or scratches, though less commonly associated with scratches than bites.
  • Capnocytophaga canimorsus infection: Typically associated with dog bites, this bacterium can also be found in cats and could potentially cause infection through a scratch, especially in immunocompromised individuals.
  • Erysipeloid: A rare infection caused by Erysipelothrix rhusiopathiae, more commonly associated with animal bites or exposure to infected animals, but could theoretically occur through a cat scratch.