Differential Diagnosis for Red Raised Rash on Chest

The patient presents with a red, raised, painful, and warm rash on the chest, and is currently taking fenofibrate, Humira, and metoprolol. Here's a differential diagnosis organized into categories:

• Single Most Likely Diagnosis
  • Drug Rash (e.g., due to fenofibrate or metoprolol): Given the patient's medication regimen, a drug rash is a plausible explanation. Both fenofibrate and metoprolol can cause skin reactions, including rashes. The timing of the rash in relation to the initiation of these medications would be crucial in determining causality.
• Other Likely Diagnoses
  • Psoriasis: Although the patient is on Humira, which is used to treat psoriasis, it's possible that the rash could be a flare of psoriasis itself, especially if the treatment is not fully effective or if there's a rebound effect.
  • Eczema/Dermatitis: Contact dermatitis or atopic dermatitis could present with a red, raised rash. The chest area could be involved due to allergens or irritants.
  • Insect Bites/Allergic Reaction: Depending on the environment and recent exposures, insect bites or an allergic reaction to something in the environment could cause a similar presentation.
• Do Not Miss Diagnoses
  • Cellulitis: A bacterial infection of the skin that can present with redness, warmth, and pain. It's crucial to distinguish this from other causes of rash due to the need for antibiotic treatment.
  • Stevens-Johnson Syndrome (SJS) or Toxic Epidermal Necrolysis (TEN): Although rare, these are life-threatening conditions that can be triggered by medications, including those the patient is taking. Early recognition is critical for management and preventing severe outcomes.
• Rare Diagnoses
  • Sweet Syndrome (Acute Febrile Neutrophilic Dermatosis): Characterized by fever, neutrophilia, and tender, erythematous skin lesions. It can be associated with infections, inflammatory bowel disease, or medications.
  • Erythema Multiforme: An immune-mediated disorder that can be triggered by infections or medications, presenting with target-like lesions. It's less common but should be considered in the differential due to its distinctive appearance and potential for serious complications.

Each of these diagnoses has different implications for treatment and patient management, emphasizing the importance of a thorough diagnostic workup.