Differential Diagnosis for Rash on Face that Worsens with Sun Exposure

• Single Most Likely Diagnosis
  • Polymorphic Light Eruption (PMLE): This is the most common photodermatosis, characterized by a rash that occurs after sun exposure. It typically appears as papules, plaques, or vesicles on sun-exposed areas, including the face.
• Other Likely Diagnoses
  • Lupus Erythematosus: Systemic lupus erythematosus (SLE) can cause a photosensitive rash, often on the face, known as a "butterfly rash." Sun exposure can exacerbate the condition.
  • Rosacea: While not exclusively caused by sun exposure, rosacea can worsen with UV radiation, leading to increased redness, papules, and pustules on the face.
  • Seborrheic Dermatitis: This condition can cause a rash on the face, which may be exacerbated by sun exposure, although it's not the primary trigger.
• Do Not Miss Diagnoses
  • Porphyria Cutanea Tarda: A rare genetic disorder that causes blistering skin lesions upon sun exposure. It's crucial to diagnose due to potential liver damage and other systemic complications.
  • Xeroderma Pigmentosum: A genetic disorder that increases sensitivity to UV light, leading to severe sunburn, blistering, and increased risk of skin cancers. Early diagnosis is critical for management and prevention of complications.
• Rare Diagnoses
  • Solar Urticaria: A rare condition where sun exposure triggers urticarial lesions (hives) within minutes of exposure.
  • Chronic Actinic Dermatitis: A rare skin condition characterized by a persistent, eczematous dermatitis in sun-exposed areas, often seen in older adults.
  • Erythropoietic Protoporphyria: Another form of porphyria that causes sensitivity to sunlight, leading to burning pain, swelling, and blistering of the skin.