Photosensitivity reactions: The Daily PANCE Blueprint
A 28-year-old woman presents to the dermatology clinic with a pruritic rash on her forearms and chest. She reports that the rash appeared after spending a day at the beach. She denies any new medications, lotions, or detergents. Physical examination shows erythematous papules and plaques on sun-exposed areas. There is no mucosal involvement. Which of the following is the most likely diagnosis?
A) Contact dermatitis
B) Polymorphous light eruption
C) Drug-induced photosensitivity
D) Solar urticaria
E) Lupus erythematosus
Answer and topic summary
The answer is B) Polymorphous light eruption
The patient’s symptoms of a pruritic rash appearing on sun-exposed areas after a day at the beach are indicative of polymorphous light eruption (PMLE). PMLE is a hypersensitivity reaction to UV radiation, often occurring in the spring or early summer when sun exposure is first increased. The rash appears as small, raised bumps that are 2–5 millimeters across. The bumps can appear in a dense formation, making the rash look similar to eczema or prickly heat. It is more common in women and usually affects areas that are not habitually exposed to sunlight. The exact cause of PMLE isn’t understood. It’s thought that the body’s immune system recognizes some components of the sun-altered skin as “foreign” and activates its immune defenses against them. PMLE usually has an autoimmune basis. Treatment often involves sun avoidance, use of broad-spectrum sunscreens, and topical corticosteroids for symptomatic relief.
Incorrect Answer Explanations:
- A) Contact dermatitis: Would likely be associated with a new product or substance and may not be limited to sun-exposed areas.
- C) Drug-induced photosensitivity: Would be associated with a new medication and may have a different rash morphology.
- D) Solar urticaria: Presents with hives rather than papules and plaques.
- E) Lupus erythematosus: Would likely have systemic symptoms and possibly mucosal involvement.
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