What is responsible for her rash?

A 69-year-old female presents with an itchy rash on the upper chest of 2 weeks duration. She does not remember any exposure history. She denies rash elsewhere and is otherwise healthy. 

What is responsible for her rash?

A. Pityrosporon folliculitis
B. Demodex folliculitis
C. Rosacea
D. Cutaneous lupus erythematosus
E. Actinic keratoses

Answer: Cutaneous lupus erythematosus   

A biopsy confirmed the diagnosis of cutaneous lupus erythematosus. This acute type of lupus is similar to that seen with systemic lupus erythematosus, without any evidence of systemic involvement upon workup as seen with this patient. Treatment is often successful with topical corticosteroids or the addition of hydroxychloroquine in more resistant cases. 

Differential diagnosis. This case looked a little like pityrosporon but she was rather “mature” to have sudden onset. Rosacea can be seen on the chest but is also typically seen on the face at the same time. Actinic keratoses are typically more keratotic. Demodex is usually more pustular.