Differential Diagnosis for Pruritic Rash
The patient presents with a pruritic/irritating rash on his right forearm and right foot, which he noticed approximately 5 days ago. He has recently purchased a new dog and has been taking it for walks. Here is a differential diagnosis for the patient's condition:
- Single most likely diagnosis
- Contact Dermatitis: This is the most likely diagnosis given the patient's recent exposure to a new dog and the location of the rash on his forearm and foot, which are common areas for contact with the dog or its environment. The lack of response to over-the-counter Benadryl stick also supports this diagnosis.
- Other Likely diagnoses
- Insect Bites: The patient's recent outdoor activities with his new dog increase the likelihood of insect bites, which can cause pruritic rashes.
- Allergic Reaction: An allergic reaction to something in the patient's environment, such as pollen or dust, could also cause a pruritic rash.
- Eczema: The patient's symptoms could also be consistent with eczema, a chronic skin condition characterized by dry, itchy skin.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Lyme Disease: Although less likely, Lyme disease is a serious condition that can cause a rash and should not be missed. The patient's recent outdoor activities increase the risk of tick exposure.
- Rocky Mountain Spotted Fever: This is another tick-borne illness that can cause a rash and should be considered in the differential diagnosis.
- Rare diagnoses
- Scabies: Scabies is a parasitic infection that can cause a pruritic rash, but it is less likely given the patient's lack of exposure to others with the condition.
- Leishmaniasis: This is a rare parasitic infection that can cause skin lesions, but it is unlikely given the patient's lack of travel history to endemic areas.