Differential Diagnosis for 54 yo Male with Metastatic Bladder Cancer and Skin Lesions

• Single Most Likely Diagnosis
  • Radiation Dermatitis: Given the patient's history of metastatic bladder cancer and lymphedema, it is likely that he has undergone radiation therapy, which can cause skin lesions, erythema, and blisters. The lack of improvement with antibiotics supports this diagnosis.
• Other Likely Diagnoses
  • Contact Dermatitis: The patient's skin lesions could be an allergic reaction to his bowel regimen, Zofran, Tigan, OxyContin, or oxycodone, or other substances he is exposed to.
  • Bullous Pemphigoid: An autoimmune skin disorder that can cause blisters and erythema, which can be associated with malignancies.
  • Drug-Induced Rash: The patient's medications, particularly OxyContin and oxycodone, can cause skin rashes and lesions.
• Do Not Miss Diagnoses
  • Toxic Epidermal Necrolysis (TEN): A life-threatening skin condition that can be caused by medications, including those the patient is taking. Although rare, it is essential to consider this diagnosis due to its high mortality rate.
  • Stevens-Johnson Syndrome: A severe skin and mucous membrane disorder that can be caused by medications and is potentially life-threatening.
  • Infection (e.g., Cellulitis, Abscess): Although the patient did not improve with antibiotics, it is crucial to consider the possibility of a resistant or unusual infection, especially in an immunocompromised patient.
• Rare Diagnoses
  • Paraneoplastic Pemphigus: A rare autoimmune disorder associated with malignancies, which can cause severe skin lesions and blisters.
  • Erythema Multiforme: A rare skin condition that can be caused by medications, infections, or other factors, and is characterized by target-like lesions.
  • Cutaneous Metastasis: Although rare, it is possible that the patient's metastatic bladder cancer has spread to the skin, causing the lesions.