Are these erythematous plaques rosacea—or something else?

 A 56-year-old man has had progressive, erythematous plaques across the forehead and temples for the past few weeks. He describes these areas as “a little itchy and a little tender.” The patient is otherwise healthy and takes no medications.

Which of the following is the most likely cause?
A. Rosacea.
B. Seborrheic dermatitis.
C. Contact dermatitis
D. Cutaneous lupus.
E. Photodermatitis.

Answer on next page 

Cutaneous lupus

A skin biopsy confirmed the diagnosis of cutaneous lupus, D; subsequent blood test results, including an antinuclear antibody assay, were normal. Rosacea commonly involves the central face but is in the differential. Seborrheic and contact dermatitides typically show more scaling and are not tender. Photodermatitis usually occurs following use of a systemic or a topical agent; this patient had no such history.

The best management option for this patient is a sunscreen that blocks the UV-A spectrum, which aggravates cutaneous lupus.