Differential Diagnosis

The patient presents with itching, rash over the upper body, and a history of temporary improvement with a short course of prednisone. The rash is described as small, circular openings on the arms, chest, and back. The patient also reports a possible reaction to a medication in a patch delivery and a new mattress that may be causing an allergy.

• Single Most Likely Diagnosis
  • Contact Dermatitis: This is the most likely diagnosis given the patient's history of a new mattress and a possible reaction to a medication patch. The rash's description and the patient's symptoms are consistent with an allergic contact dermatitis, which is a type IV hypersensitivity reaction. The temporary improvement with prednisone also supports this diagnosis, as corticosteroids are effective in reducing inflammation and itching associated with contact dermatatitis.
• Other Likely Diagnoses
  • Atopic Dermatitis (Eczema): Although less likely given the acute onset and the patient's history, atopic dermatitis is a common condition that can present with itching and rash. The patient's response to prednisone could also be seen in atopic dermatitis.
  • Drug Rash: Given the patient's history of a possible reaction to a medication patch, a drug rash is a plausible diagnosis. However, the fact that the PCP stopped the medication and the rash persisted makes this less likely.
  • Allergic Reaction to the New Mattress: An allergic reaction to materials in the new mattress could cause a rash. This could be due to various components like latex, dyes, or other chemicals used in the manufacturing process.
• Do Not Miss Diagnoses
  • Bullous Pemphigoid: Although rare, bullous pemphigoid is an autoimmune disease that can present with itching and blistering skin lesions. It's more common in older adults and can be triggered by certain medications or other factors.
  • Pemphigus Vulgaris: Another autoimmune disease that affects the skin, causing blistering lesions. It's less common but can be life-threatening if not treated properly.
  • Erythema Multiforme: A skin condition characterized by target lesions, which can be triggered by infections, medications, or other factors. It can sometimes be associated with more severe conditions like Stevens-Johnson syndrome.
• Rare Diagnoses
  • Dermatitis Herpetiformis: A rare skin condition associated with celiac disease, characterized by intensely itchy blisters. It's less likely given the patient's presentation but could be considered if other diagnoses are ruled out.
  • Pityriasis Rosea: A rare skin condition that causes a rash, often triggered by viral infections. It's characterized by a herald patch followed by a wider rash, which might fit the patient's description of small, circular openings.