Differential Diagnosis for Sun Exposed Area with Non-Blanching Papules

• Single Most Likely Diagnosis
  • Actinic Purpura: This condition is characterized by non-blanching, purple lesions that occur on sun-exposed areas, particularly in older adults. The lesions are due to blood vessel fragility and are common in areas such as the forearms and hands.
• Other Likely Diagnoses
  • Petechiae: These are small, non-blanching spots that can appear on sun-exposed areas due to various reasons including sun damage, aging, or as a side effect of certain medications.
  • Solar Lentigines (Liver Spots): While not typically papular, these flat brown or black spots can sometimes be mistaken for papules and are very common in sun-exposed areas.
  • Seborrheic Keratoses: These are benign growths that can appear as papules and are common in sun-exposed areas, though they are usually pigmented.
• Do Not Miss Diagnoses
  • Malignant Melanoma: Although less likely, any new or changing skin lesion, especially in sun-exposed areas, warrants consideration of melanoma due to its potential lethality if not caught early.
  • Vasculitis: Certain forms of vasculitis can present with non-blanching papules and should be considered, especially if there are systemic symptoms or other signs of inflammation.
• Rare Diagnoses
  • Amyloidosis: Cutaneous amyloidosis can present with papules, and while rare, it's an important consideration in the differential diagnosis of non-blanching papules in sun-exposed areas.
  • Porphyria Cutanea Tarda: This is a rare disorder that can cause blistering and scarring on sun-exposed skin, and while not typically presenting as non-blanching papules, it can have varied manifestations.